Best Objective-C Open Source Repositories

Objective-C is an object-oriented language that extends C with Smalltalk-style messaging syntax, and for decades it was the primary language for building applications on Apple's platforms, including macOS and iOS, before Apple introduced Swift in 2014 as its intended successor. It uses square-bracket message-passing syntax rather than the dot-notation method calls common in most other object-oriented languages, and it retains full interoperability with plain C, letting Objective-C code call C libraries directly without a bridging layer.

Even as Swift has become the default choice for new Apple platform development, Objective-C hasn't disappeared, largely because so much existing code, including large portions of Apple's own frameworks and countless mature third-party libraries, was originally written in it. Objective-C and Swift can coexist in the same project through bridging headers, which lets teams gradually migrate legacy codebases to Swift rather than rewriting everything at once, or simply keep stable, working Objective-C code in place indefinitely.

Cross-platform mobile frameworks in particular still rely on Objective-C for their iOS integration layers. React Native and Expo both use Objective-C in parts of their native iOS bridge code, since it interfaces directly with Apple's underlying platform APIs. Flutter also includes Objective-C in its iOS embedding layer, and OBS Studio uses it for macOS-specific screen capture and system integration code that needs direct access to native Apple frameworks.