Objective C +（id）方法

Question

我在某些方面對Objective-C很新穎，所以我想問一下我應該如何讓方法返回對象本身。讓我給個例子：

在NSArray你可以做[NSArray arrayWithObjects:bla,bla,nil];

我如何作出這樣的一種方法，以我自己的類？

Answer 1

有與該方法會在兩個主要方面：

1. 這是一個類的方法（即+方法）
2. 它使用一個變量參數列表

要使它，你可能會這樣做：

+ (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 

}