Cocoa is
Apple
An apple is an edible fruit produced by an apple tree (''Malus domestica''). Apple trees are cultivated worldwide and are the most widely grown species in the genus '' Malus''. The tree originated in Central Asia, where its wild ancest ...
's native
object-oriented
Object-oriented programming (OOP) is a programming paradigm based on the concept of "objects", which can contain data and code. The data is in the form of fields (often known as attributes or ''properties''), and the code is in the form of ...
application programming interface (API) for its
desktop operating system
An operating system (OS) is system software that manages computer hardware, software resources, and provides common daemon (computing), services for computer programs.
Time-sharing operating systems scheduler (computing), schedule tasks for ef ...
macOS
macOS (; previously OS X and originally Mac OS X) is a Unix operating system developed and marketed by Apple Inc. since 2001. It is the primary operating system for Apple's Mac computers. Within the market of desktop and la ...
.
Cocoa consists of the
Foundation Kit,
Application Kit, and
Core Data
Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0.Apple, "Core Data Tutorial for iPhone OS". It allows data orga ...
frameworks, as included by the
Cocoa.h
header file, and the libraries and frameworks included by those, such as the C standard library and the Objective-C runtime.
[Mac Technology Overview: OS X Frameworks](_blank)
Developer.apple.com. Retrieved on September 18, 2013.
Cocoa applications are typically developed using the development tools provided by Apple, specifically
Xcode
Xcode is Apple's integrated development environment (IDE) for macOS, used to develop software for macOS, iOS, iPadOS, watchOS, and tvOS. It was initially released in late 2003; the latest stable release is version 14.2, released on December 13, ...
(formerly
Project Builder
Project Builder was an integrated development environment (IDE) originally developed by NeXT for version 3 of the NeXTSTEP operating system by separating out the code editing parts of Interface Builder into its own application.
After Apple Comput ...
) and
Interface Builder (now part of Xcode), using the
programming language
A programming language is a system of notation for writing computer programs. Most programming languages are text-based formal languages, but they may also be graphical. They are a kind of computer language.
The description of a programming ...
s
Objective-C or
Swift. However, the Cocoa programming environment can be accessed using other tools. It is also possible to write Objective-C Cocoa programs in a simple
text editor and build it manually with
GNU Compiler Collection (GCC) or
Clang from the command line or from a
makefile
In software development, Make is a build automation tool that automatically builds executable programs and libraries from source code by reading files called ''Makefiles'' which specify how to derive the target program. Though integrated ...
.
For
end users, Cocoa
applications are those written using the Cocoa programming environment. Such applications usually have a familiar look and feel, since the Cocoa programming environment provides a lot of common
UI elements (such as buttons, scroll bars, etc.), and automates many aspects of an application to comply with Apple's
human interface guidelines.
For
iOS,
iPadOS,
tvOS, and
watchOS, a similar API exists, named
Cocoa Touch
Cocoa Touch is the application development environment for building software programs to run on iOS for the iPhone and iPod Touch, iPadOS for the iPad, watchOS for the Apple Watch, and tvOS for the Apple TV, from Apple Inc.
Cocoa Touch ...
, which includes
gesture recognition,
animation, and a different set of
graphical control elements. It is used in
applications for Apple devices such as the
iPhone, the
iPod Touch, the
iPad
The iPad is a brand of iOS and iPadOS-based tablet computers that are developed by Apple Inc., Apple Inc. The iPad was conceived before the related iPhone but the iPhone was developed and released first. Speculation about the development, ...
, the
Apple TV, and the
Apple Watch.
History
Cocoa continues the lineage of several
software frameworks (mainly the ''App Kit'' and ''Foundation Kit'') from the
NeXTSTEP and
OpenStep
OpenStep is a defunct object-oriented application programming interface (API) specification for a legacy object-oriented operating system, with the basic goal of offering a NeXTSTEP-like environment on non-NeXTSTEP operating systems. OpenStep wa ...
programming environments developed by
NeXT
Next may refer to:
Arts and entertainment Film
* ''Next'' (1990 film), an animated short about William Shakespeare
* ''Next'' (2007 film), a sci-fi film starring Nicolas Cage
* '' Next: A Primer on Urban Painting'', a 2005 documentary film
Lit ...
in the 1980s and 1990s. Apple acquired NeXT in December 1996, and subsequently went to work on the
Rhapsody operating system that was to be the direct successor of OpenStep. It was to have had an emulation base for
classic Mac OS applications, named ''Blue Box''. The OpenStep base of libraries and binary support was termed ''Yellow Box''. Rhapsody evolved into Mac OS X, and the Yellow Box became Cocoa. Thus, Cocoa classes begin with the letters ''NS'', such as NSString or NSArray. These stand for the original proprietary term for the OpenStep framework, NeXTSTEP.
Much of the work that went into developing OpenStep was applied to developing Mac OS X, Cocoa being the most visible part. However, differences exist. For example, NeXTSTEP and OpenStep used
Display PostScript for on-screen display of text and graphics, while Cocoa depends on Apple's
Quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
(which uses the
Portable Document Format
Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating syste ...
(PDF) imaging model, but not its underlying technology). Cocoa also has a level of Internet support, including the NSURL and
WebKit
WebKit is a browser engine developed by Apple and primarily used in its Safari web browser, as well as on the iOS and iPadOS version of any web browser. WebKit is also used by the BlackBerry Browser, PlayStation consoles beginning from the ...
HTML
The HyperText Markup Language or HTML is the standard markup language for documents designed to be displayed in a web browser. It can be assisted by technologies such as Cascading Style Sheets (CSS) and scripting languages such as JavaS ...
classes, and others, while OpenStep had only rudimentary support for managed network connections via NSFileHandle classes and
Berkeley sockets
Berkeley sockets is an application programming interface (API) for Internet sockets and Unix domain sockets, used for inter-process communication (IPC). It is commonly implemented as a library of linkable modules. It originated with the 4.2BS ...
.
The resulting software framework received the name ''Cocoa'' for the sake of expediency, because the name had already been trademarked by Apple. For many years before this present use of the name, Apple's ''Cocoa'' trademark had originated as the name of a multimedia project design application for children. The application was
originally developed at the
Apple Advanced Technology Group
The Advanced Technology Group (ATG) was a corporate research laboratory at Apple Computer from 1986 to 1997. ATG was an evolution of Apple's Education Research Group (ERG) and was started by Larry Tesler in October 1986 to study long-term res ...
under the name ''KidSim'', and was then renamed and trademarked as "Cocoa". The name, coined by Peter Jensen who was hired to develop Cocoa for Apple, was intended to evoke "Java for kids", as it ran embedded in web pages. The trademark, and thus the name "Cocoa", was re-used to avoid the delay which would have occurred while registering a new
trademark
A trademark (also written trade mark or trade-mark) is a type of intellectual property consisting of a recognizable sign, design, or expression that identifies products or services from a particular source and distinguishes them from ot ...
for this software framework. The original "Cocoa" program was discontinued at Apple in one of the
rationalizations that followed
Steve Jobs
Steven Paul Jobs (February 24, 1955 – October 5, 2011) was an American entrepreneur, industrial designer, media proprietor, and investor. He was the co-founder, chairman, and CEO of Apple; the chairman and majority shareholder of Pixar; ...
's return to Apple. It was then licensed to a third party and marketed as
Stagecast Creator
Stagecast Creator is a visual programming language intended for use in teaching programming to children. It is based on the programming by demonstration
concept, where rules are created by giving examples of what actions should take place in a gi ...
until 2014.
Memory management
One feature of the Cocoa environment is its facility for managing dynamically allocated memory.
Foundation Kit's NSObject class, from which most classes, both vendor and user, are derived, implements a
reference counting scheme for memory management. Objects that derive from the NSObject root class respond to a
retain
and a
release
message, and keep a retain count. A method titled
retainCount
exists, but contrary to its name, will usually not return the exact retain count of an object. It is mainly used for system-level purposes. Invoking it manually is not recommended by Apple.
A newly allocated object created with
alloc
or
copy
has a retain count of one. Sending that object a
retain
message increments the retain count, while sending it a
release
message decrements the retain count. When an object's retain count reaches zero, it is deallocated by a procedure similar to a C++ ''destructor''.
dealloc
is not guaranteed to be invoked.
Starting with Objective-C 2.0, the Objective-C runtime implemented an optional
garbage collector
A waste collector, also known as a garbageman, garbage collector, trashman (in the US), binman or (rarely) dustman (in the UK), is a person employed by a public or private enterprise to collect and dispose of municipal solid waste (refuse) and ...
, which is now obsolete and deprecated in favor of
Automatic Reference Counting (ARC). In this model, the runtime turned Cocoa
reference counting operations such as "retain" and "release" into
no-op
In computer science, a NOP, no-op, or NOOP (pronounced "no op"; short for no operation) is a machine language instruction and its assembly language mnemonic, programming language statement, or computer protocol command that does nothing.
Ma ...
s. The garbage collector does not exist on the
iOS implementation of Objective-C 2.0. Garbage collection in Objective-C ran on a low-priority background thread, and can halt on Cocoa's user events, with the intention of keeping the user experience responsive. The legacy garbage collector is still available on Mac OS X version 10.13, but no Apple-provided applications use it.
In 2011, the
LLVM
LLVM is a set of compiler and toolchain technologies that can be used to develop a front end for any programming language and a back end for any instruction set architecture. LLVM is designed around a language-independent intermediate repre ...
compiler introduced
Automatic Reference Counting (ARC), which replaces the conventional garbage collector by performing static analysis of Objective-C source code and inserting retain and release messages as necessary.
Main frameworks
Cocoa consists of three
Objective-C object libraries called ''
frameworks
A framework is a generic term commonly referring to an essential supporting structure which other things are built on top of.
Framework may refer to:
Computing
* Application framework, used to implement the structure of an application for an op ...
''. Frameworks are functionally similar to
shared libraries
In computer science, a library is a collection of non-volatile resources used by computer programs, often for software development. These may include configuration data, documentation, help data, message templates, pre-written code and ...
, a compiled object that can be dynamically loaded into a program's address space at runtime, but frameworks add associated resources, header files, and documentation. The Cocoa frameworks are implemented as a type of
bundle
Bundle or Bundling may refer to:
* Bundling (packaging), the process of using straps to bundle up items
Biology
* Bundle of His, a collection of heart muscle cells specialized for electrical conduction
* Bundle of Kent, an extra conduction path ...
, containing the aforementioned items in standard locations.
* ''
Foundation Kit'' (''Foundation''), first appeared in Enterprise Objects Framework on NeXTSTEP 3. It was developed as part of the OpenStep work, and subsequently became the basis for OpenStep's AppKit when that system was released in 1994. On macOS, Foundation is based on
Core Foundation
Core Foundation (also called CF) is a C application programming interface (API) written by Apple for its operating systems, and is a mix of low-level routines and wrapper functions. Most Core Foundation routines follow a certain naming conventio ...
. Foundation is a generic object-oriented library providing
string and value manipulation,
containers
A container is any receptacle or enclosure for holding a product used in storage, packaging, and transportation, including shipping.
Things kept inside of a container are protected on several sides by being inside of its structure. The ter ...
and
iteration,
distributed computing
A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another from any system. Distributed computing is a field of computer sci ...
,
event loops (run loops), and other functions that are not directly tied to the graphical user interface. The "NS" prefix, used for all classes and
constants
Constant or The Constant may refer to:
Mathematics
* Constant (mathematics), a non-varying value
* Mathematical constant, a special number that arises naturally in mathematics, such as or
Other concepts
* Control variable or scientific const ...
in the framework, comes from Cocoa's OPENSTEP heritage, which was jointly developed by NeXT and
Sun Microsystems.
* ''
Application Kit'' (''AppKit'') is directly descended from the original NeXTSTEP Application Kit. It contains code programs can use to create and interact with
graphical user interface
The GUI ( "UI" by itself is still usually pronounced . or ), graphical user interface, is a form of user interface that allows users to interact with electronic devices through graphical icons and audio indicator such as primary notation, ins ...
s. AppKit is built on top of Foundation, and uses the same ''NS'' prefix.
* ''
Core Data
Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0.Apple, "Core Data Tutorial for iPhone OS". It allows data orga ...
'' is the object persistence framework included with Foundation and Cocoa and found in Cocoa.h.
A key part of the Cocoa architecture is its comprehensive views model. This is organized along conventional lines for an application framework, but is based on the
Portable Document Format
Portable Document Format (PDF), standardized as ISO 32000, is a file format developed by Adobe in 1992 to present documents, including text formatting and images, in a manner independent of application software, hardware, and operating syste ...
(PDF) drawing model provided by
Quartz
Quartz is a hard, crystalline mineral composed of silica ( silicon dioxide). The atoms are linked in a continuous framework of SiO4 silicon-oxygen tetrahedra, with each oxygen being shared between two tetrahedra, giving an overall chemical f ...
. This allows creating custom drawing content using
PostScript-like drawing commands, which also allows automatic printer support and so forth. Since the Cocoa framework manages all the clipping, scrolling, scaling and other chores of drawing graphics, the programmer is freed from implementing basic infrastructure and can concentrate on the unique aspects of an application's content.
Model–view–controller
The
Smalltalk teams at
Xerox PARC eventually settled on a design philosophy that led to easy development and high code reuse. Named ''
model–view–controller'' (MVC), the concept breaks an application into three sets of interacting object classes:
* Model classes represent problem domain data and operations (such as lists of people/departments/budgets; documents containing sections/paragraphs/footnotes of stylized text).
* View classes implement visual representations and affordances for human-computer interaction (such as scrollable grids of captioned icons and pop-up menus of possible operations).
* Controller classes contain logic that surfaces model data as view representations, maps affordance-initiated user actions to model operations, and maintains state to keep the two synchronized.
Cocoa's design is a fairly, but not absolutely strict application of MVC principles. Under OpenStep, most of the classes provided were either high-level View classes (in AppKit) or one of a number of relatively low-level model classes like NSString. Compared to similar MVC systems, OpenStep lacked a strong model layer. No stock class represented a "document," for instance. During the transition to Cocoa, the model layer was expanded greatly, introducing a number of pre-rolled classes to provide functionality common to desktop applications.
In Mac OS X 10.3, Apple introduced the NSController family of classes, which provide predefined behavior for the controller layer. These classes are considered part of the
Cocoa Bindings system, which also makes extensive use of protocols such as
Key-Value Observing and
Key-Value Binding. The term 'binding' refers to a relationship between two objects, often between a view and a controller. Bindings allow the developer to focus more on declarative relationships rather than orchestrating fine-grained behavior.
With the arrival of Mac OS X 10.4, Apple extended this foundation further by introducing the
Core Data
Core Data is an object graph and persistence framework provided by Apple in the macOS and iOS operating systems. It was introduced in Mac OS X 10.4 Tiger and iOS with iPhone SDK 3.0.Apple, "Core Data Tutorial for iPhone OS". It allows data orga ...
framework, which standardizes change tracking and persistence in the model layer. In effect, the framework greatly simplifies the process of making changes to application data, undoing changes when necessary, saving data to disk, and reading it back in.
In providing framework support for all three MVC domains, Apple's goal is to reduce the amount of boilerplate or "glue" code that developers have to write, freeing up resources to spend time on application-specific features.
Late binding
In most object-oriented languages, calls to methods are represented physically by a pointer to the code in memory. This restricts the design of an application since specific ''command handling'' classes are needed, usually organized according to the
chain-of-responsibility pattern In object-oriented design, the chain-of-responsibility pattern is a behavioral design pattern consisting of a source of command objects and a series of processing objects. Each processing object contains logic that defines the types of command ob ...
. While Cocoa retains this approach for the most part, Objective-C's
late binding opens up more flexibility.
Under Objective-C, methods are represented by a ''selector'', a string describing the method to call. When a message is sent, the selector is sent into the Objective-C runtime, matched against a list of available methods, and the method's ''implementation'' is called. Since the selector is text data, this lets it be saved to a file, transmitted over a network or between processes, or manipulated in other ways. The implementation of the method is looked up at runtime, not compile time. There is a small performance penalty for this, but late binding allows the same selector to reference different implementations.
By a similar token, Cocoa provides a pervasive data manipulation method called ''key-value coding'' (KVC). This allows a piece of data or property of an object to be looked up or changed at runtime by name. The property name acts as a key to the value. In traditional languages, this late binding is impossible. KVC leads to great design flexibility. An object's type need not be known, yet any property of that object can be discovered using KVC. Also, by extending this system using something Cocoa terms ''key-value observing'' (KVO), automatic support for
undo-redo is provided.
Late static binding is a variant of binding somewhere between static and dynamic binding. The binding of names before the program is run is called static (''early''); bindings performed as the program runs are dynamic (''late'' or ''virtual'').
Rich objects
One of the most useful features of Cocoa is the powerful ''base objects'' the system supplies. As an example, consider the Foundation classes
NSString
and
NSAttributedString
, which provide
Unicode
Unicode, formally The Unicode Standard,The formal version reference is is an information technology standard for the consistent encoding, representation, and handling of text expressed in most of the world's writing systems. The standard, ...
strings, and the
NSText
system in AppKit, which allows the programmer to place string objects in the GUI.
NSText
and its related classes are used to display and edit strings. The collection of objects involved permit an application to implement anything from a simple single-line text entry field to a complete multi-page, multi-column text layout schema, with full professional
typography
Typography is the art and technique of arranging type to make written language legible, readable and appealing when displayed. The arrangement of type involves selecting typefaces, point sizes, line lengths, line-spacing ( leading), an ...
features such as
kerning
In typography, kerning is the process of adjusting the spacing between characters in a proportional font, usually to achieve a visually pleasing result. Kerning adjusts the space between individual letterforms, while tracking (letter-spacin ...
,
ligatures, running text around arbitrary
shapes,
rotation, full Unicode support, and
anti-aliased glyph rendering. Paragraph layout can be controlled automatically or by the user, using a built-in "
ruler" object that can be attached to any text view. Spell checking is automatic, using a system-wide set of language dictionaries. Unlimited undo/redo support is built in. Using only the built-in features, one can write a text editor application in as few as 10 lines of code. With new controller objects, this may fall towards zero.
When extensions are needed, Cocoa's use of Objective-C makes this a straightforward task. Objective-C includes the concept of
categories" which allows modifying existing class "in-place". Functionality can be accomplished in a category without any changes to the original classes in the framework, or even access to its source. In other common languages, this same task requires deriving a new subclass supporting the added features, and then replacing all instances of the original class with instances of the new subclass.
Implementations and bindings
The Cocoa frameworks are written in
Objective-C. Java
bindings for the Cocoa frameworks (termed the ''Java bridge'') were also made available with the aim of replacing Objective-C with a more popular language but these bindings were unpopular among Cocoa developers and Cocoa's message passing semantics did not translate well to a statically-typed language such as Java. Cocoa's need for runtime binding means many of Cocoa's key features are not available with Java. In 2005, Apple announced that the Java bridge was to be deprecated, meaning that features added to Cocoa in macOS versions later than 10.4 would not be added to the Cocoa-Java programming interface.
At
Apple Worldwide Developers Conference (WWDC) 2014, Apple introduced a new programming language named
Swift, which is intended to replace Objective-C.
AppleScriptObjC
Originally, AppleScript Studio could be used to develop simpler Cocoa applications. However, as of Snow Leopard, it has been deprecated. It was replaced with AppleScriptObjC, which allows programming in
AppleScript, while using Cocoa frameworks.
Other bindings
The Cocoa programming environment can be accessed using other tools with the aid of
bridge mechanisms such as
PasCocoa,
PyObjC,
CamelBones,
RubyCocoa
RubyCocoa is a macOS framework that provides a bridge between the Ruby and the Objective-C programming languages, allowing the user to manipulate Objective-C objects from Ruby, and vice versa. It makes it possible to write a Cocoa application c ...
, and a
D/Objective-C Bridge.
Third-party bindings available for other languages include
AppleScript,
Clozure CL,
Monobjc
Mono is a free and open-source .NET Framework-compatible software framework. Originally by Ximian, it was later acquired by Novell, and is now being led by Xamarin, a subsidiary of Microsoft and the .NET Foundation. Mono can be run on many soft ...
and
NObjective (
C#),
Cocoa# (CLI), Cocodao and
D/Objective-C Bridge,
LispWorks,
Object Pascal,
CamelBones (
Perl
Perl is a family of two high-level, general-purpose, interpreted, dynamic programming languages. "Perl" refers to Perl 5, but from 2000 to 2019 it also referred to its redesigned "sister language", Perl 6, before the latter's name was offic ...
),
PyObjC (
Python),
FPC PasCocoa (
Lazarus and
Free Pascal),
RubyCocoa
RubyCocoa is a macOS framework that provides a bridge between the Ruby and the Objective-C programming languages, allowing the user to manipulate Objective-C objects from Ruby, and vice versa. It makes it possible to write a Cocoa application c ...
(
Ruby
A ruby is a pinkish red to blood-red colored gemstone, a variety of the mineral corundum ( aluminium oxide). Ruby is one of the most popular traditional jewelry gems and is very durable. Other varieties of gem-quality corundum are called ...
).
A Ruby language implementation named
MacRuby
MacRuby is a discontinued implementation of the Ruby language that ran on the Objective-C runtime and CoreFoundation framework under development by Apple Inc. which "was supposed to replace RubyCocoa". It targeted Ruby 1.9 and used the high pe ...
, which removes the need for a bridge mechanism, was formerly developed by Apple, while
Nu is a
Lisp-like language that uses the
Objective-C object model directly, and thus can use the Cocoa frameworks without needing a binding.
Other implementations
There are also open source implementations of major parts of the Cocoa framework, such as
GNUstep and Cocotron,
Cocotron
free software implementation of Cocoa. which allow cross-platform
In computing, cross-platform software (also called multi-platform software, platform-agnostic software, or platform-independent software) is computer software that is designed to work in several computing platforms. Some cross-platform software ...
Cocoa application development to target other operating systems, such as Microsoft Windows
Windows is a group of several proprietary graphical operating system families developed and marketed by Microsoft. Each family caters to a certain sector of the computing industry. For example, Windows NT for consumers, Windows Server for ...
and Linux
Linux ( or ) is a family of open-source Unix-like operating systems based on the Linux kernel, an operating system kernel first released on September 17, 1991, by Linus Torvalds. Linux is typically packaged as a Linux distribution, whi ...
.
See also
References
Bibliography
*Aaron Hillegass
Aaron Hillegass (born 1969) Is the founder and former CEO of Big Nerd Ranch. Aaron is best known to many programmers as the author of ''Objective-C: The Big Nerd Ranch Guide'', ''Cocoa Programming for Mac OS X'', and ''iOS Programming: The Big Ner ...
: ''Cocoa Programming for Mac OS X'', Addison-Wesley, 3rd Edition 2008, Paperback, .
* Stephen Kochan: ''Programming in Objective-C'', Sams, 1st Edition 2003, Paperback, .
* Michael Beam, James Duncan Davidson
James Duncan Davidson is an American software developer and photographer. He's currently the Technology Advisor to Tobias Lütke, CEO of Shopify.
While a software engineer at Sun Microsystems (1997–2001), Davidson created Tomcat, a Java-bas ...
: ''Cocoa in a Nutshell'', O'Reilly, 1st Edition 2003, Paperback, .
* Erick Tejkowski: ''Cocoa Programming for Dummies'', 1st Edition 2003, Paperback, .
*
* Paris Buttfield-Addison, Jon Manning: ''Learning Cocoa with Objective-C'', O'Reilly, 3rd Edition 2012, Paperback, .
* Scott Anguish, Erik M. Buck, Donald A. Yacktman: ''Cocoa Programming'', Sams, 1st Edition 2002, Paperback, .
* Erik M. Buck, Donald A. Yacktman: ''Cocoa Design Patterns'', Addison-Wesley Professional, 1st Edition 2009, Paperback,
* Bill Cheeseman: ''Cocoa Recipes for Mac OS X'', Peachpit Press, 1st Edition 2002, Paperback, .
*Andrew Duncan: ''Objective-C Pocket Reference, O'Reilly'', 1st Edition 2002, Paperback, .
External links
*
Mac Developer Library, Cocoa Layer
Apple's documentation
iDevApps
Mac programming forum
Cocoa Dev Central
Cocoa Dev
Stack Overflow: Cocoa
{{Widget toolkits
MacOS APIs