iphone - 参数列表语法

Question

我试图理解这样的构造:

  - (void)someMethodWithArgs:(type?) param, ...
{
        ???
}

[self someMethodWithArgs:arg1, arg2, arg3];

• 如何访问参数列表？
• “type”应该是指针，还是可以是“int”？

Answer 1

Objective-C 函数的工作方式。

声明

- (void) someMethodWithArgA:(type)paramName argB:(typeB)paramNameB
{
     // do something with paramName and paramNameB 

}

调用

[self someMethodWithArgA:val argB:valB];

<小时/>

C 等效项是:

void someMethodWithArgs(type paramName, typeB paramNameB)
{
     // do something with paramName and paramNameB    
}

someMethodWithArgs(val,valB);

<小时/>

当然，与 C 一样，变量类型可以是任何(为什么它们应该只是指针？)。

<小时/>

一个简单的例子:

- (int)addNum:(int)a withNum:(int)b
{
      int c = a+b;
      return c;
}

int k = [self addNum:2 withNum:3];
// k = 5

<小时/>

引用

The Objective-C model of object-oriented programming is based on message passing to object instances. In Objective-C one does not simply call a method; one sends a message.

http://en.wikipedia.org/wiki/Objective-C#Messages

<小时/>

更新

使用可变数量的参数实现方法

#import <Cocoa/Cocoa.h>

@interface NSMutableArray (variadicMethodExample)

- (void) appendObjects:(id) firstObject, ...; // This method takes a nil-terminated list of objects.

@end

@implementation NSMutableArray (variadicMethodExample)

- (void) appendObjects:(id) firstObject, ...
{
     id eachObject;
     va_list argumentList;
     if (firstObject) // The first argument isn't part of the varargs list,
     {                                   // so we'll handle it separately.
          [self addObject: firstObject];
          va_start(argumentList, firstObject); 
          // Start scanning for arguments after firstObject.

          // As many times as we can get an argument of type "id"
          while (eachObject = va_arg(argumentList, id)) 
                 [self addObject: eachObject]; 

          va_end(argumentList);
     }
}

@end

来自:http://developer.apple.com/library/mac/#qa/qa1405/_index.html