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今天讲Objective-C的方法声明，尽管在语法上，Objective-C的方法和其它高级语言有很大不同，但是，在概念上还是很类似的。

Method Declarations Indicate the Messages an Object Can Receive

The examples so far have involved a class describing a typical model object, or an object designed primarily to encapsulate data. In the case of a Person class, it’s possible that there wouldn’t need to be any functionality beyond being able to access the two
declared properties. The majority of classes, however, do include behavior in addition to any declared properties.

Given that Objective-C software is built from a large network of objects, it’s important to note that those objects can interact with each other by sending messages. In Objective-C terms, one object sends a message to another object by calling a method on that
object.

Objective-C methods are conceptually similar to standard functions in C and other programming languages, though the syntax is quite different. A C function declaration looks like this:

void SomeFunction();

The equivalent Objective-C method declaration looks like this:
- (void)someMethod;

In this case, the method has no parameters. The C void keyword is used inside parentheses at the beginning of the declaration to indicate that the method doesn’t return any value once it’s finished.

The minus sign (-) at the front of the method name indicates that it is an instance method, which can be called on any instance of the class. This differentiates it from class methods, which can be called on the class itself, as described in Objective-C Classes
Are also Objects.

As with C function prototypes, a method declaration inside an Objective-C class interface is just like any other C statement and requires a terminating semi-colon.