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我正在尝试使用 API 类从 URL 获取数据，然后将该数据返回到 ViewController 内的方法。我让 ViewController 调用 API 方法。

已经在 SO 上尝试了几个地方并提出了以下建议，但它不起作用，作为一个 Objective-C 菜鸟已经尝试阅读文档等，但仍然不明白可能出了什么问题。

我有一个视图控制器在类“api”中调用方法“fetch”。
我在 api 类中有连接委托，它工作正常（在connectionDidFinishLoading方法中打印了正确的数据）。
我需要一个委托将数据返回给 viewcontroller 类中的方法。

到目前为止我有

视图控制器.h

#import "Api.h"

@interface ViewController : UIViewController <apiDelegate>{

}

- (void)apiSucceeded:(NSString *)jsonString;
- (void)apiFailed:(NSString *)failedMessage;

@end

视图控制器.m

#import "ViewController.h"
#import "Api.h"

- (void)apiSucceeded:(NSString *)jsonString {
    NSLog(@"WORKED");
}
- (void)apiFailed:(NSString *)failedMessage {
    NSLog(@"FAILED");
}
- (void)viewDidLoad {
    [super viewDidLoad];
    Api* myapi = [[Api alloc]init]; 
    [myapi fetch]; 
}
@end

api.h

@protocol apiDelegate
@required
- (void)apiSucceeded:(NSString *)jsonString;
- (void)apiFailed:(NSString *)failedMessage;
@end


@interface Api : NSObject {
    id _delegate;

}
@property (nonatomic, assign) id _delegate;

-(void)fetch;
@end

api.m

#import "Api.h"
#import "ViewController.h" 

@synthesize _delegate; 

- (void)fetch{  

//connection setup....
[NSURLConnection connectionWithRequest:[request autorelease] delegate:self];

}


-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    [self.receivedData setLength: 0];
}
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    //  NSLog(@"append data");
    [self.receivedData appendData:data];
    // NSLog(@"Bytes: %d", [receivedData length]);
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error
{
    //TODO error handling for connection
    if ([_delegate respondsToSelector:@selector(apiFailed:)]) {
        [_delegate apiFailed:[error localizedDescription]];
    }
    NSLog(@"Cannot Connect");
}
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSLog(@"DONE. Received Bytes: %d", [self.receivedData length]);

    NSString *jsonString = [[NSString alloc] initWithBytes: [receivedData mutableBytes] length:[receivedData length] encoding:NSUTF8StringEncoding];


    if ([_delegate respondsToSelector:@selector(apiSucceeded:)])    {
        [_delegate apiSucceeded:jsonString];
    }

}

@end

没有错误，但它只是不运行 'apiSucceeded' 方法。
请不要将此误解为有关“connectionDidFinishLoading”的问题。那一点效果很好，它将数据返回给导致问题的 ViewController。

任何人都可以看到我做错了什么吗？

4

1 回答 1

2

我好像你忘了设置

myapi.delegate = self;

后

Api* myapi = [[Api alloc]init];
于 2013-04-01T19:01:15.163 回答