Learn objective c mac pdf
An object wishing to implement forwarding needs only to override the forwarding method with a new method to define the forwarding behavior. The action method performv:: need not be overridden, as this method merely performs an action based on the selector and arguments. When compiled using gcc , the compiler reports:. The compiler is reporting the point made earlier, that Forwarder does not respond to hello messages. In this circumstance, it is safe to ignore the warning since forwarding was implemented. Running the program produces this output:. During the design of Objective-C, one of the main concerns was the maintainability of large code bases.
Experience from the structured programming world had shown that one of the main ways to improve code was to break it down into smaller pieces. Objective-C borrowed and extended the concept of categories from Smalltalk implementations to help with this process. Furthermore, the methods within a category are added to a class at run-time. Thus, categories permit the programmer to add methods to an existing class - an open class - without the need to recompile that class or even have access to its source code.
For example, if a system does not contain a spell checker in its String implementation, it could be added without modifying the String source code. Methods within categories become indistinguishable from the methods in a class when the program is run. A category has full access to all of the instance variables within the class, including private variables. If a category declares a method with the same method signature as an existing method in a class, the category's method is adopted.
Thus categories can not only add methods to a class, but also replace existing methods. This feature can be used to fix bugs in other classes by rewriting their methods, or to cause a global change to a class's behavior within a program. If two categories have methods with the same name but different method signatures, it is undefined which category's method is adopted.
Other languages have attempted to add this feature in a variety of ways. TOM took the Objective-C system a step further and allowed for the addition of variables also. Other languages have used prototype-based solutions instead, the most notable being Self. The C and Visual Basic. NET languages implement superficially similar functionality in the form of extension methods , but these lack access to the private variables of the class.
Logtalk implements a concept of categories as first-class entities that subsumes Objective-C categories functionality Logtalk categories can also be used as fine-grained units of composition when defining e. This example builds up an Integer class, by defining first a basic class with only accessor methods implemented, and adding two categories, Arithmetic and Display , which extend the basic class.
Become an Xcoder: Start Programming the Mac Using Objective-C
While categories can access the base class's private data members, it is often good practice to access these private data members through the accessor methods, which helps keep categories more independent from the base class. Implementing such accessors is one typical usage of categories. Another is to use categories to add methods to the base class. However, it is not regarded as good practice to use categories for subclass overriding, also known as monkey patching.
Informal protocols are implemented as a category on the base NSObject class. The program will still run. This means that it is possible to mix-and-match added categories if needed; if a category does not need to have some ability, it can simply not be compile in. Objective-C permits a class to wholly replace another class within a program.
The replacing class is said to "pose as" the target class. Class posing was declared deprecated with Mac OS X v Similar functionality can be achieved by using method swizzling in categories, that swaps one method's implementation with another's that have the same signature. For the versions still supporting posing, all messages sent to the target class are instead received by the posing class. There are several restrictions:. Posing, similarly with categories, allows global augmentation of existing classes.
Posing permits two features absent from categories:. In the C language, the include pre-compile directive always causes a file's contents to be inserted into the source at that point. Objective-C has the import directive, equivalent except that each file is included only once per compilation unit, obviating the need for include guards. Objective-C's features often allow for flexible, and often easy, solutions to programming issues. As nothing is done to unify the semantics behind the various language features, certain restrictions apply:.
Mac OS X v GCC 4. When run in backwards-compatible mode, the runtime turned reference counting operations such as "retain" and "release" into no-ops. All objects were subject to garbage collection when garbage collection was enabled. The garbage collector does not exist on the iOS implementation of Objective-C 2. Garbage collection was deprecated in Mac OS X v Properties are, in a sense, public instance variables; that is, declaring an instance variable as a property provides external classes with access possibly limited, e.
A property may be declared as "readonly", and may be provided with storage semantics such as assign , copy or retain. By default, properties are considered atomic , which results in a lock preventing multiple threads from accessing them at the same time. A property can be declared as nonatomic , which removes this lock. Properties are implemented by way of the synthesize keyword, which generates getter and setter, if not read-only methods according to the property declaration.
Alternatively, the getter and setter methods must be implemented explicitly, or the dynamic keyword can be used to indicate that accessor methods will be provided by other means.
When compiled using clang 3. In order to use dot notation to invoke property accessors within an instance method, the "self" keyword should be used:. A class or protocol's properties may be dynamically introspected. Under the modern runtime, an extra layer of indirection is added to instance variable access, allowing the dynamic linker to adjust instance layout at runtime. This feature allows for two important improvements to Objective-C code:. In Objective-C 2. Fast enumeration generates more efficient code than standard enumeration because method calls to enumerate over objects are replaced by pointer arithmetic using the NSFastEnumeration protocol.
A class extension has the same syntax as a category declaration with no category name, and the methods and properties declared in it are added directly to the main class. It is mostly used as an alternative to a category to add methods to a class without advertising them in the public headers, with the advantage that for class extensions the compiler checks that all the privately declared methods are actually implemented. Since fast enumeration does not generate exactly the same binaries as standard enumeration, its use will cause an application to crash on Mac OS X version Blocks are only supported in Mac OS X Automatic Reference Counting ARC is a compile-time feature that eliminates the need for programmers to manually manage retain counts using retain and release.
Xcode can also attempt to automatically upgrade a project to ARC. Using this format saves the programmer from having to use the longer initWithString or similar methods when doing certain operations. However, different from string literals , which compile to constants in the executable, these literals compile to code equivalent to the above method calls.
In particular, under manually reference-counted memory management, these objects are autoreleased, which requires added care when e. In code, subscripting is represented using brackets [ ]. After the purchase of NeXT by Apple, attempts were made to make the language more acceptable to programmers more familiar with Java than Smalltalk. One of these attempts was introducing what was dubbed "Modern Syntax" for Objective-C at the time  as opposed to the current, "classic" syntax. There was no change in behaviour, this was merely an alternative syntax.
Instead of writing a method invocation like. It also includes a runtime library called ObjectPak, which is based on Cox's original ICPak library which in turn derives from the Smalltalk class library , and is quite radically different from the OpenStep FoundationKit. Objective-C today is often used in tandem with a fixed library of standard objects often known as a "kit" or "framework" , such as Cocoa , GNUstep or ObjFW. These libraries often come with the operating system: the GNUstep libraries often come with Linux -based distributions and Cocoa comes with macOS.
Objective-C allows for the declaration of new root classes that do not inherit any existing functionality. Originally, Objective-C-based programming environments typically offered an Object class as the base class from which almost all other classes inherited. With the introduction of OpenStep, NeXT created a new base class named NSObject, which offered additional features over Object an emphasis on using object references and reference counting instead of raw pointers, for example.
Almost all classes in Cocoa inherit from NSObject. Not only did the renaming serve to differentiate the new default behavior of classes within the OpenStep API, but it allowed code that used Object—the original base class used on NeXTSTEP and, more or less, other Objective-C class libraries —to co-exist in the same runtime with code that used NSObject with some limitations. The introduction of the two letter prefix also became a simplistic form of namespaces, which Objective-C lacks. Using a prefix to create an informal packaging identifier became an informal coding standard in the Objective-C community, and continues to this day.
More recently, package managers have started appearing, such as CocoaPods , which aims to be both a package manager and a repository of packages. A lot of open-source Objective-C code that was written in the last few years can now be installed using CocoaPods. Objective-C implementations use a thin runtime system written in C [ citation needed ] , which adds little to the size of the application.
In contrast, most object-oriented systems at the time that it was created used large virtual machine runtimes. Programs written in Objective-C tend to be not much larger than the size of their code and that of the libraries which generally do not need to be included in the software distribution , in contrast to Smalltalk systems where a large amount of memory was used just to open a window. Since the programmer has such freedom to delegate, forward calls, build selectors on the fly and pass them to the runtime system, the Objective-C compiler cannot assume it is safe to remove unused methods or to inline calls.
Likewise, the language can be implemented atop extant C compilers in GCC , first as a preprocessor, then as a module rather than as a new compiler. This allows Objective-C to leverage the huge existing collection of C code, libraries, tools, etc. In this aspect, it is similar to GObject library and Vala language, which are widely used in development of GTK applications.
All of these practical changes lowered the barrier to entry , likely the biggest problem for the widespread acceptance of Smalltalk in the s. A common criticism is that Objective-C does not have language support for namespaces. It can get a bit tedious to write these all out if you have many properties, but don't be tempted to avoid this, because hiding the implementation is much more important in the long run. The setText:withSize: method is a little more complex, since we need to retain and release objects. We'll be covering this in detail in the next chapter, so don't worry about it for now.
However, this is required most times that you are using objects as properties of other objects, which will happen a lot. This signals to Cocoa that the view content has changed and should be redrawn. Cocoa makes a note of that and will cause our drawRect: method to get called in due course, so anyone who makes use of the setText:withSize: method of our view will see those new settings appear immediately.
The initWithFrame: method also sets these various data members to some default values, so that the object will work even if nobody ever comes along and sets the text, its size, etc. Every object has an init method whose purpose is to establish the object's default properties so that it will function properly right out of the box. Sometimes, objects will need parameters sent to the init method, so a different version of an init method is needed, as the way initWithFrame: was coded. Note that the init method's first job is to call the superclass's initWithFrame: method.
This happens all the way back up the chain of ancestor classes until everyone has initialized what it knows about. So there are two main rules to follow when writing your init method:. The init method must return 'self' as its result, provided that the super's initialization succeeded. If not, it will return nil and so should you. If your own initialization fails, but your super's succeeded, you should return nil also.
This indicates to the caller that something went wrong while making your object. More about this later. This means two different things. In the first place, it means that you can have different methods that differ only according to their parameter types, and the correct one will be called according to what you're passing. The right one is called depending on whether you pass an int or a float. While handy, this can get confusing, especially when automatic type conversion is taking place, as it frequently does between simple scalar values. Objective-C doesn't support this type of potentially ambiguous polymorphism.
Instead, because parameters are an inherent part of a method's name, you can make it much clearer, e. There is no ambiguity, since you have to name which one you mean explicitly. The second kind of polymorphism is dynamic polymorphism. We have already seen this in action in our simple program.
It calls our object as if it were an NSView. The method call resolves to our custom object however, and so our code gets called, allowing it to do its thing. All object-oriented languages need to support this kind of polymorphism, so the fact that Objective-C does too is no surprise. What is different is that Objective-C resolves the method at runtime. For the typical case, this runtime binding makes no difference.
It safely allows us to use anonymous objects, and even null objects. It allows us to create a delayed method call called an invocation that can be used later, and it permits things like Undo to be implemented much more easily. It greatly helps us create a graphical user interface for our code, because commands, actions and so on of various window controls can be made extremely general. Let's suppose we have an object that must respond to a click on a button in a window.
Really, the button shouldn't need to care which sort of object it is controlling, only that when it is clicked, it should do something. Let's suppose a method exists called action: , and the button knows that it should call this on an object called 'target' when clicked. In a traditional language, the target object's type must be known to the button, so that it can determine if a method called action: really exists. Once that type is indicated to the button, it can only ever deal with objects of that type, or their subclasses.
However, in Objective-C, we could hook up totally unrelated objects to the button, and as long as they implemented action: , they would respond to the button. This is a great improvement in flexibility. An 'anonymous' object has a type of 'id'. Anywhere you see 'id' used as an object type, an anonymous object reference is created. In Objective-C, the value nil has a type of id.
This means that nil is an object! This chapter shows how to create these custom views. Chapter 8 Introduces the event loop and explains how events propagate along the responder chain. It also covers how events are queued and dispatched, as well as how event delegation works. Chapter 9 Shows how to work with the data-bearing objects of an application. The chapter also shows how this information can be utilized with the Controllers and Views of an application and how it can be read from and written to storage.
Part III Many applications today, such as word processors and web browsers, are built around the concept of a document. Creating an application that can handle multiple documents is. Luckily, Cocoa provides the ability for an application to handle multiple documents with ease. Document-Based Applications shows how to use Cocoa's document architecture.
Chapter 10 Presents the basic concepts of the document-handling architecture and how documents are managed. The chapter guides you through the process of creating an application that takes advantage of the architecture. Chapter 11 Shows advanced text-handling abilities of Cocoa, such as handling fonts, working with layout managers, enabling rulers, and working with attachments.
Part IV Miscellaneous Topics covers a variety of Mac OS X and Cocoa features that are important to delivering finished applications and giving them their finishing touches. The chapters in this part of the book cover diverse topics and can be read in any order. Chapter 12 This chapter shows you how to add printing functionality to your application. Chapter 13 Here we describe how bundles, application or otherwise, are structured, how icons and document types are defined, and how application signatures work. Chapter 14 Once you build an application, there are several ways to customize the interface to accommodate users in different parts of the world.
Chapter 15 Mac OS X provides comprehensive management of user preferences. This chapter explains how to work with this system to store information that can be used across multiple invocations of your application. Applications will often have more than just one interface component. Inspectors and palettes abound in modern applications. This chapter shows in detail how to store your user interface in multiple nib files to improve performance and ease maintainability and localization.
Chapter 17 Once you build an application, there are several important things you should do to make it ready for distribution. Cocoa provides default copyright strings and About boxes that need to be edited, and you should probably create some sort of Help documentation for the application. Finally, this chapter shows how to create an icon for your application and add that to the application bundle as well. Part V The Appendixes include quick-reference material for learning more about Cocoa's Objective-C classes and list resources that are beyond the scope of this book for expanding your Cocoa development horizon.
Appendix A Provides solutions to all of the exercises found at the end of each chapter. Appendix B Provides a valuable list of Cocoa-related resources and where to find them, including Mac OS X's "built-in" developer documentation, books, mailing lists, and web sites. Appendix C Provides a guide to the various API references available to you as a developer, as well as some tools that will help you search and browse the available documentation.
How to Use This Book Our recommendation is that you read this book from cover to cover, particularly if you're new to Cocoa and need to learn more about object-oriented programming OOP. As you read through the book, you should work on the sample programs along the way. We try to take the approach of teaching you small things first and then building on those small concepts throughout the rest of the book.
If you have experience with Java or Smalltalk, we recommend that you read this book from front to back as well. Since you have experience with object-oriented concepts and programming, there are some sections that you will be able to skim. However, be careful not to skim too fast, as you might miss some important details.
Conventions Used in This Book The following is a list of the typographical conventions used in this book: Italic Used to indicate new terms, URLs, filenames, file extensions, directories, commands and options, program names, and to highlight comments in examples.
Constant Width Used to show code examples, the contents of files, or the output from commands. Constant Width Bold Used in examples and tables to show commands or other text that should be typed literally. Constant Width Italic Used in examples and tables to show text that should be replaced with usersupplied values. Arrows are used to signify a navigation path when using window Login Login Items means that options; for example, System Preferences you would launch System Preferences, click the icon for the Login control panel, and select the Login Items pane within that panel. Pathnames Pathnames are used to show the location of a file or application in the filesystem.
Directories or folders are separated by a forward slash. For example, if you see something like, ". A carriage return at the end of a line of code is used to denote an unnatural line break; that is, you should not enter these as two lines of code, but as one continuous line. Multiple lines are used in these cases due to printing constraints. Menu Symbols When looking at the menus for any application, you will see some symbols associated with keyboard shortcuts for a particular command.
You should pay special attention to notes set apart from the text with the following icons: This is a tip, suggestion, or general note. It contains useful supplementary information about the topic at hand. This indicates a warning or caution. It will help you solve and avoid annoying problems. How to Contact Us We have tested and verified the information in this book to the best of our ability, but you may find that features have changed or even that we have made mistakes!
As a newcomer to Cocoa and a reader of this book, you can help us to improve future editions by sending us your feedback. Please let us know about any errors, inaccuracies, bugs, misleading or confusing statements, and typos that you find anywhere in this book. Please also let us know what we can do to make this book more useful to you. We take your comments seriously and will try to incorporate reasonable suggestions into future editions.
To be put on the mailing list or to request a catalog, send email to: info oreilly. Acknowledgments First and foremost, I'd like to thank my editor, Chuck Toporek, who talked me into writing the new edition of this book twice even and alternately utilized the editor's whip and kind words of encouragement to guide me toward its completion. Without him, his advice, and his faith in me to get the job done, this book would not have happened. Thanks as well to all the people at Apple, especially to the original NeXT and Apple documentation teams.
For this new edition, we've changed the title, stripped the book down to bare metal, and built it back up. Without the foundation provided by the original documentation teams, the job would have been much harder. Also thanks to the many Cocoa engineers at Apple for taking the time to hash over the outline for the revision, and for reviewing drafts of the manuscript along the way. You guys know who you are. Many thanks to the independent reviewers of this book, including Jo Davidson who gave up part of the Memorial Day weekend to help us meet our deadlines and Mike Barron.
Special thanks to Jason Hunter, who gave me an author's insight into the writing process, for helping me find the right metaphors in Chapter 3, and for always being there when needed. In addition, many thanks to Wilfredo Snchez Vega, who got me hooked on Mac OS X in the first place after my Windows laptop went through one of its periodic meltdowns.
Music from many creative and talented people fueled the writing of this book. And finally, thanks to all my family and friends who lent support to the book writing process and who encouraged me to chase my dreams: Dad, who taught me everything I needed to know after all; Mom, who brought me into the world; Mahaila, who probably never expected that I-of all the people in the family-would write a book; my sisters Susan, Illona, Joli, and Heather, as well as my friends Justyna Horwat and Jim Driscoll. Last, but not least, I want to thank Eleo, who ended up thoroughly addicted to the wireless network I.
Part I: Cocoa Overview and Foundation This part of the book introduces the Cocoa frameworks Foundation and Application Kit and describes the high-level features they provide application programmers, as well as how they fit with other Mac OS X frameworks. It also includes a brief introduction to object-oriented programming, the Objective-C language, and Apple's Developer Tools. Chapters in this part of the book include: Chapter 1 Chapter 2 Chapter 3 Chapter 4. Chapter 1. Introduction to Cocoa Cocoa provides a rich layer of functionality on which you can build applications. Still others come from the original Macintosh environment and have been updated to work with a modern operating system.
In many cases, you take advantage of these underlying technologies transparently, and you get the use of them essentially "for free. As a transitional API, Carbon gives developers a clear way to migrate legacy . Adobe Photoshop 7. X are both examples of "Carbonized" applications. Programming with the Cocoa API is the focus of this book. Java A robust and fast virtual-machine environment for running applications developed using the Java Development Kit.
Java applications are typically very portable and can run unchanged, without recompilation, on many different computing environments. A command-line environment also exists as part of this layer. Classic The compatibility environment in which the system runs applications originally. Classic is essentially a modified version of Mac OS 9 running inside a process that has special hooks into other parts of the operating system.
Over time, Classic is becoming less interesting as more applications are ported to run natively in Mac OS X. To some degree, all of these application environments rely on other parts of the system. Figure gives a layered, albeit simplified, illustration of Mac OS X's application environments and their relationship to the other primary parts of the operating system. Figure Cocoa as part of Mac OS X's programming environment. As you can see from Figure , each of Mac OS X's application environments relies upon functionality provided by deeper layers of the operating system.
This functionality is roughly broken into two major sections: Core Foundation, which provides a common set of application and core services to the Cocoa, Carbon, and Java frameworks, and the kernel environment, which is the underlying Unix-based core of the operating system. Contrary to what you may have heard elsewhere, Carbon is not doomed to fade away over time. This erroneous opinion seems to be caused by a misinterpretation of the word "transitional" to mean that the API itself will be going away, rather than meaning it is the API to use to transition older applications.
Moving forward, it will remain one of the core development environments for Mac OS X. In fact, Apple engineers are striving to enable better integration between Carbon and Cocoa. It is an integrated set of shared object libraries, a runtime system, and a development environment. Cocoa provides most of the infrastructure that graphical user applications typically need and insulates those applications from the internal workings of the core operating system.
Think of Cocoa as a layer of objects acting as both mediator and facilitator between programs that you build and the operating system. These objects span the spectrum from simple wrappers for basic types, such as strings and arrays, to complex functionality, such as distributed computing and advanced imaging. They are designed to make it easy to create a graphical user interface GUI application and are based on a sophisticated infrastructure that simplifies the programming task.
Cocoa-based applications are not just limited to using the features in the Cocoa frameworks. And . It was, and continues to be, solid technology based on a design that was years ahead of anything else in the market. It utilized Display PostScript from Adobe - allowing the same code, using the PostScript page description language - to display documents on screen and to print to paper.
In NeXT exited the hardware business to concentrate on software. Other ports were performed for the. Later, the frameworks and tools were revised to run on other operating systems, such as Windows and Solaris. These revised frameworks became known as OpenStep. Fast forward to Apple had been working unsuccessfully on a next-generation operating system, known as Copland, to replace the venerable Mac OS 7. Their efforts were running amok and they decided to look outside for the foundation of the new OS.
The leading contender seemed to be BeOS, but in a surprise move, Apple acquired NeXT, citing its strengths in development software and operating environments for both the enterprise and Internet markets. As part of that evolution, OpenStep became Cocoa. Its full power, however, is available to you, the programmer, to utilize.
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Not only can you take advantage of the power, you can actually look under the hood and see how it all works. Cocoa also provides utilities for memory management, utilities for archiving and serializing objects, and access to kernel entities and services such as tasks, ports, run loops, timers, threads, and locks. On top of this foundation, Cocoa provides a set of user-interface widgets with quite a bit of built-in functionality. This functionality includes such expected things as undo and redo, drag and drop, and copy and paste, as well as lots of bonus features such as spell checking that can be enabled in any Cocoa component that accepts text.
You will see how much of this functionality works while you work through the tutorials in this book. Unlike previous versions of Mac OS, the same code and frameworks are used to draw the onscreen image and to send output to printers. You'll get firsthand experience drawing with Quartz in Chapter 7, and with printing in Chapter Apple's color management and matching technology, ColorSync, is built into Quartz, ensuring that colors in documents are automatically color-corrected for any.
Any time an image is displayed in a Cocoa window or printed, its colors are automatically rendered correctly according to any color profile embedding in the image along with profiles for the display or printer. Internationalization and localization Cocoa's well-designed internationalization architecture allows applications to be localized easily into multiple languages.
Cocoa keeps the user-interface elements separate from the executable, enabling multiple localizations to be bundled with an application. The underlying technology is the same that is used by Mac OS X to . Because Cocoa uses Unicode as its native character set, applications can easily handle all the world's living languages.
The use of Unicode eliminates many character-encoding hassles. To help you handle non-Unicode text, Cocoa provides functionality to help you translate between Unicode and the other major character sets in use today. Text and fonts Cocoa offers a powerful set of text services that can be readily adapted by textintensive applications. These services include kerning, ligatures, tab formatting, and rulers, and they can support text buffers as large as the virtual memory space.
The text system also supports embedded graphics and other inline attachments. You'll work this text system firsthand in Chapter Cocoa supports a variety of font formats, including the venerable Adobe PostScript including Types 1, 3, and 42 , the TrueType format defined by Apple in the late s and adopted by Microsoft in Windows 3.
Exported application services Cocoa applications can make functionality available to other applications, as well as to end users, through two mechanisms: scripting with AppleScript and via Services. AppleScript enables users to control applications directly on their system, including the operating system itself. Scripts allow even relatively unskilled users to automate common tasks and afford skilled scripters the ability to combine multiple applications to perform more complex tasks. For example, a script that executes when a user logs in could open the user's mail, look for a daily news summary.
Scripts have access to the entire Mac OS X environment, as well as other applications. For example, a script can launch the Terminal application, issue a command to list the running processes, and use the output for some other purpose. Services, available as a submenu item of the application menu, allow users to use functionality of an application whenever they need to. For example, you can highlight some text in an application and choose the "Make New Sticky Note" service. This functionality is not limited to text; it can work with any data type.
Component technologies One of the key advantages of Cocoa as a development environment is its capability to develop programs quickly and easily by assembling reusable components. With the proper programming tools and a little work, you can build Cocoa components that can be packaged and distributed for use by others. End-user applications are the most familiar use of this component technology in action. Other examples include the following:. Bundles containing executable code and associated resources that programs can load dynamically Frameworks that other developers can use to create programs Palettes containing custom user-interface objects that other developers can drag and drop into their own user interfaces.
Cocoa's component architecture allows you to create and distribute extensions and plug-ins easily for applications. In addition, this component architecture enables Distributed Objects, a distributed computing model that takes unique advantage of Cocoa's abilities. Mac OS X Apple might add to or modify this list at any time. These layers fit into the system as shown in Figure The Cocoa frameworks in the system.
The classes in Cocoa's Foundation framework provide objects and functionality that are the basis, or "foundation," of Cocoa and that do not have an impact on the user interface. The AppKit classes build on the Foundation classes and furnish the objects and behavior that your users see in the user interface, such as windows and buttons; the classes also handle things like mouse clicks and keystrokes.
One way to think of the difference in the frameworks is that Cocoa's Foundation classes provide functionality that operates under the surface of the application, while the AppKit classes provide the functionality for the user interface that the user sees. It is the language that we will work with throughout this book.
It is a superset of ANSI C with a few syntax and runtime extensions that make object-oriented programming possible. It started out as just a C preprocessor and a library, but over time developed into a complete runtime system, allowing a high degree of dynamism and yielding large benefits. Objective-C's syntax is uncomplicated, adding only a small number of types, preprocessor directives, and compiler directives to the C language, as well as defining a handful of conventions used to interact with the runtime system effectively.
You can also mix standard C code with Objective-C code, allowing you to choose when to do something in an object-oriented way and when to stick to procedural programming techniques by defining a structure and some functions, rather than a class. Combining Objective-C code with standard C code also lets you take advantage of existing C-based libraries. This is useful when you need functionality that is not available in Objective-C, are using libraries provided by a third party, or even reusing some of your own old code.
Objective-C is a very dynamic language. The compiler throws very little information away, which allows the runtime to use this information for dynamic binding and other uses. We'll be covering the basics of Objective-C in Chapter 3. Since its introduction to the public in , Java has gained a large following of programmers and has become a very important language in enterprise computing. Cocoa provides a set of language bindings that allow you to program Cocoa applications using Java. Apple provides Java packages corresponding to the Foundation and Application Kit frameworks.
This allows scripters to set up workflow solutions that combine the power of many applications. AppleScript combines an Englishlike language with many powerful language features, including list and record manipulation. Coverage of AppleScript Studio is beyond the scope of this book. In addition, the Foundation framework provides several paradigms that define consistent conventions for memory management and traversing collections of objects.
These conventions allow you to code more efficiently and effectively by using the same mechanisms with various kinds of objects. Two examples of these conventions are standard policies for object ownership who is responsible for disposing of objects and a set of standard abstract classes that enumerate over collections.
Figure shows the major groupings into which the Foundation classes fall. Features of the Foundation framework. The root object class, NSObject Classes representing basic data types, such as strings and byte arrays. Collection classes for storing other objects Classes representing system information and services. It also furnishes several classes whose purpose is to hold other objects-the array and dictionary collections classes.
You'll learn more about these data types-and how to use them-throughout the chapters in this book, starting in Chapter 4. String objects contain Unicode characters rather than the narrow range of characters afforded by the ASCII character set, allowing them to contain characters in any language, including Chinese, Arabic, and Hebrew. The string classes provide an API to create both mutable and immutable strings and to perform string operations such as substring searching, string comparison, and concatenation.
String scanners take strings and provide methods for extracting data from them. While scanning, you can change the scan location to rescan a portion of the string or to skip ahead a certain number of characters. Scanners can also consider or ignore case. Collections Collections allow you to organize and retrieve data in a logical manner. The collections classes provide arrays using zero-based indexing, dictionaries using keyvalue pairs, and sets that can contain an unordered collection of distinct or nondistinct elements.
The collection classes can grow dynamically, and they come in two forms: mutable and immutable. Mutable collections, as their name suggests, can be modified programmatically after the collection is created. Immutable collections are locked after they are created and cannot be changed. Data and values Data and value objects let simple allocated buffers, scalar types, pointers, and structures be treated as first-class objects. Data objects are object-oriented wrappers for byte buffers and can wrap data of any size.
When the data size is more than a few memory pages, virtual memory management can be used. Data objects contain no information about the data itself, such as its type; the responsibility for how to.
For typed data, there are value objects. These are simple containers for a single data item. They can hold any of the scalar types, such as integers, floats, and characters, as well as pointers, structures, and object addresses, and allow object-oriented manipulation of these types. They can also provide functionality such as arbitrary precision arithmetic. Dates and times Date and time classes offer methods for calculating temporal differences, displaying dates and times in any desired format, and adjusting dates and times based on location i.
Exception handling An exception is a special condition that interrupts the normal flow of program execution. Exceptions let programs handle exceptional error conditions in a graceful manner. For example, an application might interpret saving a file in a write-protected directory as an exception and provide an appropriate alert message to the user. These services all work together to create a robust environment in which your application can run.
Run loops The run loop is the programmatic interface to objects managing input sources. A run loop processes input for sources such as mouse and keyboard events from the window system, ports, timers, and other connections. Each thread has a run loop automatically created for it. When an application is started, the run loop in the default thread is started automatically. Run loops in threads that you create must be started manually.
We'll talk about run loops in detail in Chapter 8. Notifications The notification-related classes implement a system for broadcasting notifications of changes within an application. An object can specify and post a notification, and any other object can register itself as an observer of that notification.
This topic will also be covered in Chapter 8. All threads share the virtual-memory address space and communication rights of their task. When a thread is started, it is detached from its initiating thread and runs independently. Different threads within the same task can run on different CPUs in systems with multiple processors. Locks A lock is used to coordinate the operation of multiple threads of execution within the same application. A lock can be used to mediate access to an application's global data or to protect a critical section of code, allowing it to run atomicallymeaning that, at any given time, only one of the threads can access the protected resource.
Tasks Using tasks, your program can run another program as a subprocess and monitor that program's execution. A task creates a separate executable entity; it differs from a thread in that it does not share memory space with the process that creates it. Ports A port represents a communication channel to or from another port that typically resides in a different thread or task. These communication channels are not limited to a single machine, but can be distributed over a networked environment. Timers Timers are used to send a message to an object at specific intervals.
For example, you could create a timer to tell a window to update itself after a certain time interval. You can think of a timer as the software equivalent of an alarm clock. Memory management Memory management ensures that objects are properly deallocated when they are no longer needed. This mechanism, which depends on general conformance to a policy of object ownership, automatically tracks objects that are marked for release. Understanding memory management is important in creating successful Cocoa applications.
We'll discuss this critical topic in depth in Chapter 4. Serialization and archiving Serializers make it possible to represent the data that an object contains in an architecture-independent format, allowing the sharing of data across applications. A specialized serializer, known as a Coder, takes this process a step further by storing class information along with the object.
Archiving stores encoded objects and other data in files, to be used in later runs of an application or for distribution. This topic will also be covered in depth in Chapter 4. Distributed objects Cocoa provides a set of classes that build on top of ports and enable an interprocess messaging solution. This mechanism enables an application to make one or more of its objects available to other applications on the same machine or on a remote machine.
Distributed objects are an advanced topic and are not covered in this book. File management Cocoa provides a set of file-management utilities that allow you to create directories and files, extract the contents of files as data objects, change your current working location in the filesystem, and more. Besides offering a useful range of functionality, the file-management utilities insulate an application from the underlying filesystem, allowing the same functionality to be used to work with files on a local hard drive, a CD-ROM, or across a network.
URLs can be used to refer to files and are the preferred way to do so. Cocoa objects that can read or write data from or to a file can usually accept a URL, in addition to a pathname, as the file reference. Cocoa applications can also be made responsive to AppleScript commands. These classes implement the functionality needed to efficiently draw the user interface to the screen, communicate with video cards and screen buffers, and handle events from the keyboard and mouse.
Learning the many classes in the AppKit may seem daunting at first. However, you won't need to learn every feature of every class. Most of the AppKit classes are support classes that work behind the scenes helping other classes operate and with which you will not have to interact directly. Figure shows how AppKit classes are grouped and related. The Application Kit framework's features. You can create and manage windows, dialog boxes, pop-up lists, and other controls.
We'll cover these topics in depth starting in Chapter 6. Windows The two principle functions of a window are to provide an area in which views can be placed and to accept and distribute to the appropriate view events that the user creates through actions with the mouse and keyboard. Windows can be resized, minimized to the Dock, and closed. Each of these actions generates events that can. Views A view is an abstract representation for all objects displayed in a window. Views provide the structure for drawing, printing, and handling events.
Views are arranged within a window in a nested hierarchy of subviews. Panels Panels are a type of window used to display transient, global, or important information. For example, a panel should be used, rather than a window, to display error messages or to query the user for a response to remarkable or unusual circumstances.
These common panels give the user a consistent look and feel for performing common operations. Controls and widgets Cocoa provides a common set of user-interface objects such as buttons, sliders, and browsers, which you can manipulate graphically to control some aspect of your application. Just what a particular item does is up to you. Cocoa provides menus, cursors, tables, buttons, sheets, sliders, drawers, and many other widgets. As you'll find throughout this book, the Cocoa development tools provide quite a lot of assistance in making your applications behave according to Apple's Human Interface Guidelines.
Text and fonts Text can be entered into either simple text fields or into larger text views. Text fields allow entry for a single line of text, while a text view is something that you might find in a text-editing application. Text views also add the ability to format text with a variety of fonts and styles. We'll see the text-handling capabilities of. Cocoa in action in Chapter Images Images encapsulate graphics data, allowing you easy and efficient access to images stored in files on the disk and displayed on the screen. We'll work a bit with images in Chapter Color Color is supported by a variety of classes representing colors and color views.
There is a rich set of color formats and representations that automatically handle different color spaces. The color support classes define and present panels and views that allow the user to select and apply colors. Document architecture Document-based applications, such as word processors, are some of the more common types of applications developed. In contrast to applications such as iTunes, that need only a single window to work, document-based applications require sophisticated window-management capabilities. Various Application Kit classes provide an architecture for these types of applications, simplifying the work you must do.
CSE - Cocoa Programming
These classes divide and orchestrate the work of creating, saving, opening, and managing the documents of an application. We'll cover the document architecture in depth in Chapter Printing The printing classes work together to provide the means for printing the information displayed in your application's windows and views. You can also create a PDF representation of a view. You'll see how to print in Chapter Pasteboards The pasteboard is a repository for data that is copied from your application, and it makes this data available to any application that cares to use it.
The pasteboard. The Application Kit handles all the details of tracking the mouse and displaying a dragged representation of the data. Accessing the filesystem File wrappers correspond to files or directories on disk. A file wrapper holds the contents of a file in memory so it can be displayed, changed, or transmitted to another application. It also provides an icon for dragging the file or representing it as an attachment. The Open and Save panels also provide a convenient and familiar interface to the filesystem.
Spellchecking A built-in spell server provides spellchecking facilities for any application that wants it, such as word processors, text editors, and email applications. Any text field or text view can provide spellchecking by using this service. We'll enable spellchecking in an application we build in Chapter Cocoa Development Tools Getting started with Cocoa requires that quite a few concepts be presented at once.
Since a book is a linear construction, we have had to make some choices as to what pieces to present first. In order to get your hands dirty using the tools, we chose to introduce Apple's Development Tools first as a way to get you started in building your first Cocoa application. You'll see some concepts here that will be glossed over. Don't worry; we will revisit them as we go. For now, though, just go along for the ride and try not to pay too much attention to the details we're saving for later. They decided to provide their development tools to every Mac user for free.
These tools allow development of Carbon- and Cocoa-based applications, system libraries, BSD command-line utilities, hardware device drivers, and even kernel extensions. We'll be focusing on two of these tools to develop Cocoa-based applications throughout the book: Project Builder for editing, compiling, and debugging source code, and Interface Builder for laying out the graphical user interface GUI components for the application. By default, the tools aren't installed, as most users won't use them and probably want the almost MB of disk space for something else.
But developers can easily find them and install them from a variety of sources. And, since they are free, any user who wants to try developing software can do so by investing only the time it takes to learn. You can quickly check to see if you have the Developer Tools installed. Apple's development tools in the filesystem. The Developer Tools installation file. From this page you can download the Developer Tools either in segments or in one big chunk. If you download the Tools in segments, simply double-click on the first segment.
Stuff-It will launch and put all the segments together into one file. Membership in the Apple Developer Connection has its privileges. There are many levels of membership available. The free online membership gets you a good range of benefits, including access to the latest version of the Developer Tools and the ability to track bugs that you submit. These updates, which have been appearing at a rate of two to three times a year, introduce new features, fix bugs, and improve the available documentation. The only downside is that updates can be rather large. Despite the size, you should budget some time to download and use the latest versions from the ADC web site.
You should be aware of this if you're thinking that you can use Software Update as a way to ensure that you have the latest set of Tools. If you don't have a high-speed connection, you can get Apple to send you the latest copy of the Developer Tools CD at a nominal charge. Log in to the ADC member web site, and go to the Purchase section.
Since these applications are going to be used throughout this book-and hopefully throughout your future as a Mac developer-having quick access to the apps in your Dock can save you a lot of time navigating through the Finder. If you don't know how to add an application to your Dock, it's actually quite simple.
Find your way to the application you want to add, then simply drag its icon to the Dock.
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It manages software-development projects and orchestrates and streamlines the development process. Project Builder's key features include the following:. A project browser that manages all the resources of a project, allowing you to view, edit, and organize your source files. The ability to invoke the build system to build your projects and run the resulting program.
A graphical source-level debugger that allows you to walk through the code, set breakpoints, and examine call stacks. Project search capabilities that allow you to find strings anywhere in a project. CVS enables development teams local or distributed to work together easily on the same source code base.
Project Builder's main window is shown in Figure Project Builder's main window. Double-click the icon. If this is the first time that you have started Project Builder, you will be presented with an Assistant to set up your application preferences.