摘要： A class extension allows you to declare a method that is private to the classsee “Extensions” in The Objective-C Programming Language). 阅读全文

摘要： Verify Object Capabilities at RuntimeIntrospection, a powerful and useful feature of Objective-C and the NSObject class, enables you to learn certain things about objects at runtime. You can thus avoid mistakes in your code such as sending a message to an object that doesn’t recognize it or assuming 阅读全文