Cocoa Basics

As with all application environments, Cocoa presents two faces; it has a runtime aspect and a development aspect. In its runtime aspect, Cocoa applications present the user interface and are tightly integrated with the other visible portions of the operating system; on Mac OS X, these include the Finder, the Dock, and other applications from all environments.
But it is the development aspect that is the more interesting one to programmers. Cocoa is an integrated suite of object-oriented software components—classes—that enables you to rapidly create robust, full-featured Mac OS X applications. These classes are reusable and adaptable software building blocks; you can use them as-is or extend them for your specific requirements. Cocoa classes exist for just about every conceivable development necessity, from user-interface objects to data formatting, and where a need hasn’t been anticipated, you can easily create a subclass of an existing class that answers that need.
Cocoa has one of the most distinguished pedigrees of any object-oriented development environment. From its introduction as NeXTSTEP in 1989 to the present day, it has been continually refined and tested . Its elegant and powerful design is ideally suited for the rapid development of software of all kinds, not only applications but command-line tools, plug-ins, and various types of bundles. Cocoa gives your application much of its behavior and appearance “for free,” freeing up more of your time to work on those features that are distinctive.

You may use several programming languages when developing Cocoa software, but the essential, required language is Objective-C. Objective-C is a superset of ANSI C that has been extended with certain syntactical and semantic features (derived from Smalltalk) to support object-oriented programming. The few added conventions are simple and easy to learn and use. Because Objective-C rests on a foundation of ANSI C, you can freely intermix straight C code with Objective-C code. Moreover, your code can call functions defined in non-Cocoa programmatic interfaces, such as the BSD library interfaces in /usr/include. You can even mix C++ code with your Cocoa code and link them into the same executable.

he most important Cocoa class libraries come packaged in two core frameworks for each platform: Foundation and Application Kit for Mac OS X and Foundation and UIKit for iPhone OS. As with all frameworks, these contain not only a dynamically sharable library (or sometimes several compatibility versions of libraries), but header files, API documentation, and related resources. The duo of both Application Kit and Foundation and UIKit and Foundation reflect the division of the Cocoa programmatic interfaces into those classes that have some bearing on a graphical user interface and those that don’t. For each platform, its two core frameworks are essential to any Cocoa project whose end product is an application. Both platforms additionally support the Core Data framework, which is as important and useful as the core frameworks. Mac OS X also ships with several other frameworks that publish Cocoa programmatic interfaces, such as the Screen Saver and Address Book frameworks; more Cocoa frameworks will be added to the operating system over time.

what is cocoa environment

Cocoa is an application environment for both the Mac OS X operating system and iPhone OS, the operating system used on multi-touch devices such as iPhone and iPod touch. It consists of a suite of object-oriented software libraries, a runtime, and an integrated development environment.
This content expands on this definition, describing the purpose, capabilities, and components of Cocoa on both platforms. Reading this functional description of Cocoa is an essential first step toward understanding Cocoa as a developer.
 Cocoa is a set of object-oriented frameworks that provides a runtime environment for applications running on Mac OS X and iPhone OS. It is also part of a development environment that helps you efficiently bring these applications from design stage to deployment. Cocoa is the preeminent application environment for Mac OS X and the only application environment for iPhone OS. (Carbon is an alternative environment on Mac OS X, but it is a compatibility framework with procedural programmatic interface intended to support existing Mac OS X code bases.) Most of the applications you see on Mac OS X and iPhone OS, including Mail and Safari, are Cocoa applications. An integrated development environment called Xcode supports application development for both platforms. The combination of this development environment and Cocoa makes it easy to create a well-factored, full-featured application.

cocoa guide

To a developer new to it, Cocoa might seem like a vast, uncharted new world of technology. The features, tools, concepts, designs, terminology, programming interfaces, and even programming language of this development environment may all be unfamiliar. Cocoa  Guide eases the initial steps to Cocoa proficiency. It provides an orientation to the technological landscape that is Cocoa. It introduces its features, basic concepts, terminology, architectures, and underlying design patterns.
You can build Cocoa applications for two platforms: the Mac OS X operating system and iPhone OS, the operating system for multi-touch devices such as iPhone and iPod touch. Cocoa  Guide presents Cocoa-related information for both platforms, integrating the information as much as possible and pointing out platform differences when necessary. The intent is that, as you become familiar with Cocoa for one platform, it will become easier to transfer that knowledge to software development for the other platform.
Cocoa  Guide is structured to lead gradually to a general understanding of what Cocoa development is all about. It starts with the most basic information—what Cocoa is in terms of its components and capabilities—and ends with an examination of the major architectures. Each chapter builds on what was explained in previous chapters. Each section gives the important details about a subject, yet describes it at only a high level. A section frequently refers the reader to another document that offers a more comprehensive description.
In the set of Cocoa developer documentation, Cocoa  Guide is the conceptual entry-point document. It is prerequisite reading for other essential Cocoa guides, such as Cocoa Drawing Guide, View Programming Guide for Cocoa, and Cocoa Fundamentals Guide assumes little in terms of prerequisite reading, but readers should be proficient C programmers and should be familiar with the capabilities and technologies of each platform. For Mac OS X, you can acquire this familiarity by reading Mac OS X Technology Overview; for iPhone OS.