Objective-C
Objective-C is a general-purpose, object-oriented programming language that adds Smalltalk-style messaging to the C programming language. It was the primary language used by Apple for macOS and iOS development before the introduction of Swift, and it remains widely used in legacy codebases and some modern applications. The language is known for its dynamic runtime, which enables features like dynamic typing and method swizzling.
Developers should learn Objective-C if they are working on or maintaining Apple ecosystem applications, especially older iOS or macOS projects where it is still prevalent. It is essential for understanding legacy codebases, debugging issues in mixed Swift-Objective-C environments, and for developers who need to interface with low-level Apple frameworks that are written in or heavily use Objective-C. Knowledge of Objective-C is also valuable for those contributing to open-source projects in the Apple domain.