Objective-C

Objective-C
Name	Objective-C
Paradigm	Object-oriented programming, reflective programming
Designer	Brad Cox, Tom Love
Developer	Apple Inc.
Typing	Static typing, dynamic typing, weak typing
Influenced by	C (programming language), Smalltalk
Influenced	Swift (programming language), Java (programming language)

Objective-C. It is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C (programming language). Developed in the early 1980s, it became the primary language for NeXT and later for Apple Inc.'s macOS and iOS operating systems, powering a vast ecosystem of applications. Its unique blend of C (programming language) syntax with dynamic runtime capabilities made it a cornerstone of Apple Inc.'s software development for decades.

History

The language was created in the early 1980s by Brad Cox and Tom Love at their company Stepstone. They aimed to integrate the object-oriented paradigms of Smalltalk with the power and ubiquity of the C (programming language). Its adoption was significantly boosted when Steve Jobs's company NeXT licensed and used it as the foundation for their NeXTSTEP operating system. Following Apple Inc.'s acquisition of NeXT in 1996, the NeXTSTEP environment evolved into macOS and later iOS, cementing its status. The open-source implementation, GNUstep, also helped maintain its presence outside the Apple Inc. ecosystem.

Syntax and language features

Its syntax is a superset of C (programming language), meaning any valid C (programming language) program is also valid. Object-oriented features are added using square brackets for messaging, a concept borrowed directly from Smalltalk. It supports features like categories (programming) and protocols (object-oriented programming), which allow for extending existing classes and defining interfaces, respectively. Unlike C++, it uses dynamic typing extensively, with the `id` keyword representing a generic object pointer, facilitating its flexible runtime behavior.

Runtime system

A defining characteristic is its dynamic runtime system, known as the Objective-C runtime. This runtime library, central to implementations like those from Apple Inc. and GNUstep, handles messaging, class creation, and method dispatch. It enables features such as dynamic binding, introspection (computer science), and message passing at runtime, allowing for great flexibility. The runtime's ability to modify classes and methods dynamically supported technologies like Key-Value Observing and underpinned many Cocoa (API) design patterns.

Memory management

For many years, it relied on manual reference counting, where developers explicitly used `retain` and `release` methods to manage object lifecycle. This model was later augmented with Automatic Reference Counting, a compile-time feature introduced by Apple Inc. that automated memory management while avoiding the overhead of a garbage collection (computer science) system. The transition to Automatic Reference Counting significantly reduced common programming errors and was a major evolution in the language's toolchain within Xcode.

Development tools and frameworks

The primary integrated development environment for development is Xcode, which includes the Clang compiler and the LLVM compiler infrastructure. The main application programming interface frameworks are Cocoa (API) for macOS and Cocoa Touch for iOS. These frameworks provide a rich set of classes for building graphical user interfaces, handling data, and interacting with system services. Other important tools and libraries in the ecosystem include Interface Builder, Foundation Kit, and Core Data.

Adoption and legacy

It saw its peak adoption as the principal language for developing applications for iPhone, iPad, and Mac computers, creating a multi-billion dollar App Store (iOS) economy. Its influence is evident in the design of successor languages like Swift (programming language), which Apple Inc. introduced in 2014 to offer modern syntax and safety features. While the prominence of Swift (programming language) has grown, a vast codebase written in it remains in active use, and understanding it is crucial for maintaining legacy systems within the Apple Inc. software universe.

Category:Programming languages Category:Object-oriented programming languages Category:Apple Inc. software