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

1 - (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

 1 //.h  
 2 - (NSString *)addMoreArguments:(NSString *)firstStr,...NS_REQUIRES_NIL_TERMINATION;  
 3   
 4 //.m  
 5 - (NSString *)addMoreArguments:(NSString *)firstStr,...  
 6 {  
 7     va_list args;  
 8     va_start(args, firstStr); // scan for arguments after firstObject.  
 9       
10     // get rest of the objects until nil is found  
11     NSMutableString *allStr = [[[NSMutableString alloc] initWithCapacity:16] autorelease];  
12     for (NSString *str = firstStr; str != nil; str = va_arg(args,NSString*)) {  
13         [allStr appendFormat:@"* %@ ",str];  
14     }  
15       
16     va_end(args);  
17     return allStr;  
18 }  
19   
20 //test  
21 NSString *str = [self addMoreArguments:@"hello",@"world",@"this",@"is",@"a",@"test", nil];  
22 NSLog(@"str = %@",str);  
23 //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:

 1 #import <Cocoa/Cocoa.h>  
 2   
 3 @interface NSMutableArray (variadicMethodExample)  
 4   
 5 - (void) appendObjects:(id) firstObject, ...; // This method takes a nil-terminated list of objects.  
 6   
 7 @end  
 8   
 9 @implementation NSMutableArray (variadicMethodExample)  
10   
11 - (void) appendObjects:(id) firstObject, ...  
12 {  
13 id eachObject;  
14 va_list argumentList;  
15 if (firstObject) // The first argument isn't part of the varargs list,  
16   {                                   // so we'll handle it separately.  
17   [self addObject: firstObject];  
18   va_start(argumentList, firstObject); // Start scanning for arguments after firstObject.  
19   while (eachObject = va_arg(argumentList, id)) // As many times as we can get an argument of type "id"  
20       [self addObject: eachObject]; // that isn't nil, add it to self's contents.  
21   va_end(argumentList);  
22   }  
23 }  
24   
25 @end

 

posted @ 2014-01-19 21:11  ubersexual  阅读(1210)  评论(0)  编辑  收藏  举报