在 Objective-C 中实现委托模式 [英] Implementing Delegate Pattern in Objective-C

问题描述

我正在构建一个处理 NSURLConnection 请求的类.为了允许其他类使用这个类，我想允许主类在触发 connectionDidFinishLoading 时调用委托.

I am building a class that handles NSURLConnection requests. To allow other classes to use this class, I would like to allow the main class to call a delegate when connectionDidFinishLoading is fired.

我查看了很多文档，但找不到任何提供任何明确示例的内容，并且我拥有的代码由于某种原因没有调用委托.我到目前为止的代码是(代码不相关已删除):

I've looked through lots of documentation, but I can't find anything that gives any clear examples, and the code that I have doesn't call the delegate for some reason. The code I have so far is (code not relevant removed):

界面:

@interface PDUrlHandler : NSObject {
id delegate;
}
- (void)searchForItemNamed:(NSString *)searchQuery;
@property (nonatomic, assign) id delegate;
@end
@interface NSObject (PDUrlHandlerDelegate) 
- (void)urlHandler:(PDUrlhandler*)urlHandler searchResultsFinishedLoading:(NSDictionary *)resultData;
@end

实施:

- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
    NSLog(@"Fininshed Loading...");
    resultData = [self parseJSON:jsonData];

    if(delegate && [delegate respondsToSelector:@selector(urlHandler:searchResultsFinishedLoading:)]) {
        NSLog(@"Delegating!");
        [delegate urlHandler:self searchResultsFinishedLoading:resultData];
    } else {
        NSLog(@"Not Delegating. I dont know why.");
    }   

}

另一个类中的委托:

- (void)urlHandler:(PDUrlhandler*)urlHandler searchResultsFinishedLoading:(NSDictionary *)resultData;
{
    NSLog(@"Delegating!!!!");
}

推荐答案

原来我忘记设置委托了:

Turns out I forgot to set the delegate:

[currentHandler setDelegate:self];

需要在对 PDUrlHandler 进行初始调用的行之后.

needed to go after the line that makes the initial call to the PDUrlHandler.

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