多个代表收听uisearchbar的一个实例

Question

有没有办法让多个对象侦听UISearchbBar实例的void委托方法？

例如，如何UISearchDisplayController知道搜索条具有其文本串中改变：

– searchDisplayController:shouldReloadTableForSearchString: 

而在同一时间实例中，搜索显示控制器可搜索的代表表视图控制器酒吧，并知道文字是否改变？

Answer 1

@interface MultiplexingSearchBarDelegate : NSObject<UISearchBarDelegate> { 
    NSMutableArray* delegates; 
} 

- (void) addDelegate: (id) theDelegate; 
- (void) removeDelegate: (id) theDelegate; 
@end 

@implementation MultiplexingSearchBarDelegate 

- (id) init { 
    if ((self = [super init])) { 
     delegates = [[NSMutableArray alloc] initWithCapacity: 16]; 
    } 
} 

- (void) dealloc { 
    [delegates release]; 
    [super dealloc] 
} 

- (void) addDelegate: (id) theDelegate { 
    @synchronized(delegates) { 
     if (theDelegate && ! [delegates containsObject: theDelegate]) { 
      [delegates addObject: theDelegate]; 
     } 
    } 
} 

- (void) removeDelegate: (id) theDelegate { 
    @synchronized(delegates) { 
     if (theDelegate && [delegates containsObject: theDelegate]) { 
      [delegates removeObject: theDelegate]; 
     } 
    } 
} 

//add your UISearchBarDelegate methods here, following a pattern like this 
- (void)searchBar:(UISearchBar *)searchBar textDidChange:(NSString *)searchText { 
    @synchronized(delegates) { 
     for (id<UISearchBarDelegate> theDelegate in delegates) { 
      [theDelegate searchBar:searchBar textDidChange:searchText]; 
     } 
    } 
} 

@end 

然后，只需设置一个MultiplexingSearchBarDelegate为UISearchBar的代表，并直接添加委托给MultiplexingSearchBarDelegate而不是向UISearchBar。

Answer 2

只有一个对象可以是委托并接收委托方法调用。然而，委托可以通过你写的委托协议来通知许多对象。你可能需要重构一下。