多個委托監聽uisearchbar的實例

Question

有沒有一種方法可以讓多個對象偵聽UISearchbBar實例的void委托方法？

例如，UISearchDisplayController如何知道搜索欄的文本字符串已更改為：

– searchDisplayController:shouldReloadTableForSearchString:

同時，作為搜索顯示控制器實例的表視圖控制器可以成為搜索欄的委托，並且知道文本是否已更改？

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，只需將MultiplexingSearchBarDelegate設置為UISearchBar的委托，然后將您的委托添加到MultiplexingSearchBarDelegate而不是直接添加到UISearchBar 。

Answer 2

只能有一個對象作為委托並接收委托方法調用。 但是，委托可以根據您的喜好通知許多對象，也許通過您編寫的委托協議。 您可能需要重構一點。