Question

我在某些方面对Objective-C很新，所以我想问一下如何制作返回对象本身的方法。让我举个例子：

在NSArray中，您可以执行[NSArray arrayWithObjects:bla,bla,nil];

我如何为自己的班级制作这种方法？

Answer 1

该方法有两个主要方面：

这是一种类方法（即+方法）
它使用可变参数列表

要做到这一点，你可能会做这样的事情：

+ (id)fooWithStuff:(id)stuff, ... NS_REQUIRES_NIL_TERMINATION {
  // the "+" means it's a class method
  // the "NS_REQUIRES_NIL_TERMINATION" is so that the compiler knows you have to use it like this:
  // foo = [ThisClass fooWithStuff:thing1, thing2, thing3, nil];
  // (IOW, there must be a "nil" at the end of the list)

  va_list args;  // declare a "variable list"
  va_start(args, stuff);  // the list starts after the "stuff" argument

  Foo *foo = [[Foo alloc] init];  // create a Foo object

  id nextStuff = stuff;  // this is the next stuff
  while(nextStuff != nil) { // while there is more stuff...
    [foo doSomethingWithStuff:nextStuff];  // do something with the stuff
    nextStuff = va_arg(args, id);  // get the next stuff in the list
    // the "id" means that you're asking for something the size of a pointer
  }
  va_end(args);  // close the argument list

  return [foo autorelease];  // return the Foo object

}

Objective C +（id）方法

1 个答案: