Question

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。我有ViewController调用API方法。

已经在SO上尝试了几个地方，并提出了以下内容，但是它没有用，而且作为一个Objective-C noobie尝试过阅读文档，但仍然没有理解可能出现的问题。

我有一个viewcontroller在类'api'中调用方法'fetch' 我在api类中有连接委托，它工作正常（正确的数据打印在connectionDidFinishLoading方法内）我需要一个委托将数据返回到viewcontroller类中的方法。

到目前为止我已经

了

ViewController.h

#import "Api.h"

@interface ViewController : UIViewController <apiDelegate>{

}

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

@end

ViewController.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，但它没有运行'apiSucceeded'方法。
请不要误解这是关于'connectionDidFinishLoading'的问题。这一点运行良好，它将数据BACK传递给导致问题的ViewController。

有人能看到我做错了吗？

Answer 1

我似乎忘了设置

myapi.delegate = self;

后

Api* myapi = [[Api alloc]init];

ConnectionDidFinishLoading和Delegate的Objective-C问题

1 个答案: