在Objective-C中实现代理模式 [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connectionDidFinishLoading被触发时调用一个委托。

我看过很多文档，但是我找不到任何明确例子的东西，而且由于某些原因，我没有调用代码。我现在的代码是（代码不相关）：

接口：

 code> @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 *）连接{
 NSLog（@Fininshed Loading ...）; 
 resultData = [self parseJSON：jsonData]; 
 
 if（delegate&&&[] delegate responsesToSelector：@selector（urlHandler：searchResultsFinishedLoading :)]）{
 NSLog（@Delegating！）; 
 [delegate urlHandler：self searchResultsFinishedLoading：resultData]; 
} else {
 NSLog（@不委派，我不知道为什么）; 
} 
 
} 
  

其他类中的代理：

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

解决方案

原来我忘了设置代表：

  [currentHandler setDelegate：self]; 
  

需要执行初始调用PDUrlHandler的行。

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.

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):

Interface:

@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

Implementation:

- (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.");
    }   

}

The delegate within the other class:

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

解决方案

Turns out I forgot to set the delegate:

[currentHandler setDelegate:self];

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

这篇关于在Objective-C中实现代理模式的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！