Objective-C Protocols and Categories
Objective-C Protocols and Categories
Introduction
Protocols and categories are fundamental Objective-C features for defining interfaces and extending behavior. Protocols declare method contracts that classes can adopt, enabling polymorphism and delegation patterns. Categories extend existing classes with new methods without subclassing or source access.
Protocols serve similar purposes to Java interfaces or Swift protocols, enabling multiple inheritance of behavior through composition. Categories are unique to Objective-C, allowing developers to organize code, add functionality to system classes, and split large implementations across multiple files.
This skill covers formal protocols, optional methods, protocol composition, categories, class extensions, and best practices for modular Objective-C design.