iOS 多参数 ...NS_REQUIRES_NIL_TERMINATION 的写法

1.很早就看到项目里面有下面这样的写法

 - (id) initWithTitle:(NSString *)title items:(MXContextMenuItem *)item, ... NS_REQUIRES_NIL_TERMINATION;

2.查了点资料，自己练习了下，试着写了个

 //.h
 - (NSString *)addMoreArguments:(NSString *)firstStr,...NS_REQUIRES_NIL_TERMINATION;

 //.m
 - (NSString *)addMoreArguments:(NSString *)firstStr,...
 {
     va_list args;
     va_start(args, firstStr); // scan for arguments after firstObject.

     // get rest of the objects until nil is found
     NSMutableString *allStr = [[[NSMutableString alloc] initWithCapacity:16] autorelease];
     for (NSString *str = firstStr; str != nil; str = va_arg(args,NSString*)) {
         [allStr appendFormat:@"* %@ ",str];
     }

     va_end(args);
     return allStr;
 }

 //test
 NSString *str = [self addMoreArguments:@"hello",@"world",@"this",@"is",@"a",@"test", nil];
 NSLog(@"str = %@",str);
 //output: str = * hello * world * this * is * a * test

3.

官方有个例子挺好的，实现NSMutableArray的appendObjects...

appendObjects实现

code:

 #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.
   while (eachObject = va_arg(argumentList, id)) // As many times as we can get an argument of type "id"
       [self addObject: eachObject]; // that isn't nil, add it to self's contents.
   va_end(argumentList);
   }
 }

 @end