Chapter 8. Dynamic typing and runtime type information


This chapter covers
  • Static versus dynamic typing
  • Messaging
  • Runtime type information and implementation


Objective-C is a class-based object system in which each object is an instance of a particular class. At runtime, each object is aware of its class by way of a pointer named isa that points to a Class object (take a look in the debugger window the next time you’re stuck at a breakpoint, and you should see isa listed in the variable window). The class object describes the data requirements for an instance of the class and its behavior in the form of the instance methods it implements.

Objective-C is also an inherently dynamic environment. As many decisions as possible are delayed ...

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