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