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