NSURLConnection验证

Question

我正在尝试验证连接是否成功，但得到的结果不稳定。当我尝试使用伪造的url执行同步请求时：

NSData *responseData = [NSURLConnection sendSynchronousRequest:request returningResponse:&response error:&error];

if (responseData)   
    {  
        did_send = TRUE;  
    }   
    else   
    {  
        did_send = FALSE;
    }

它挂起了一段时间，并最终返回：

 did_send = FALSE;

但是如果我使用一个伪造的url进行异步请求：

NSURLConnection *conn=[[NSURLConnection alloc] initWithRequest:request delegate:self ];
if (conn)   
    {  
        did_send = TRUE;  
    }   
    else   
    {  
        did_send = FALSE;
    }

我得到了：

did_send = TRUE;

每次都是这样。我需要让异步请求工作，因为我能够设置超时，并且在请求超时时不需要挂起60秒，而默认的超时持续时间对于异步请求是不可更改的。有什么想法吗？

Answer 1

尝试使用nsurlconnection类的委托方法connection:didFailWithError:，这样可以得到一致的结果。

-(void)getLocationsFromWebService {
    NSLog(@"in getLocationsFromWebService");


    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:TRUE];


    NSURLRequest *theRequest = [NSURLRequest requestWithURL:self.locationsURL cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:100.0];

    NSURLConnection *theConnection = [[NSURLConnection alloc] initWithRequest:theRequest delegate:self];
    self.requestType = @"GET";
    if (theConnection) {
        _responseData = [[NSMutableData data] retain ];
    } else {

        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:FALSE];
    }
}
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {

    [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:FALSE]; 
    NSLog(@"in mapviewcontroller");
    NSLog(@"Error connecting - %@",[error localizedDescription]);
    [connection release];
    [_responseData release];
}

-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {

    NSHTTPURLResponse *HTTPResponse = (NSHTTPURLResponse *)response;
    NSInteger statusCode = [HTTPResponse statusCode];

    if (404 == statusCode || 500 == statusCode) {
        //[self.controller setTitle:@"Error Getting Parking Spot ....."];
        [[UIApplication sharedApplication] setNetworkActivityIndicatorVisible:FALSE];

        [connection cancel];
        NSLog(@"Server Error - %@", [NSHTTPURLResponse localizedStringForStatusCode:statusCode]);
    } else {
        if ([self.requestType isEqualToString:@"GET"])
            [_responseData setLength:0];
    }
}

-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data {
    if ([self.requestType isEqualToString:@"GET"])
        [_responseData appendData:data];
}

-(void) connectionDidFinishLoading:(NSURLConnection *)connection {

    if ([self.requestType isEqualToString:@"GET"]) {
        [self parseLocations:_responseData];
        [_responseData release];
    }
    [connection release];

}

Answer 2

简单地实例化NSURLConnection不会做任何事情。它创建该类的一个实例，但不开始数据传输--即使请求不可能得到满足，对象通常也是非空的。

相反，委托对象(代码中的self)需要实现NSURLConnectionDelegate (它将处理诸如“传入数据”或“错误条件”之类的回调)。然后，您必须向NSURLConnection实例发送-start消息，该消息将在正在执行的线程的run循环中调度它。

有关NSURLConnectionDelegate协议的更多信息(包括如何在回调中执行的信息)，请参阅苹果的“URL Loading System Programming Guide”。