What are the types of method call dispatching in Objective-C?

In Objective-C, there are several types of method call dispatching:

1. Dynamic Dispatch — the main mechanism where the method call is determined at runtime. This allows overriding methods in subclasses and using polymorphism.

2. Static Dispatch — the method call is determined at compile time. In Objective-C, this is rare, for example, when calling C functions or methods declared as static.

3. Message Passing — in Objective-C, a method call is implemented as sending a message to an object (objc_msgSend). This allows intercepting calls, dynamically changing behavior, and implementing mechanisms like method swizzling.

Thus, the main and unique mechanism for Objective-C is message passing, which provides flexibility and dynamism in calls.