Question

是否有办法让多个对象侦听UISearchbBar实例的void委托方法？

例如，UISearchDisplayController如何知道搜索栏的文本字符串已更改：

– searchDisplayController:shouldReloadTableForSearchString:

同时在表视图控制器中，搜索显示控制器的实例可以是搜索栏的代理并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

然后只需设置一个MultiplexingSearchBarDelegate作为UISearchBar的代表，并将您的代表添加到MultiplexingSearchBarDelegate，而不是直接添加到UISearchBar。

Answer 2

只有一个对象可以作为委托并接收委托方法调用。但是，代理可以根据您的喜好通知许多对象，也许可以通过您编写的委托协议。你可能需要重构一下。

不止一个代表听一个uisearchbar的实例

2 个答案: