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。当我尝试使用虚假网址执行同步请求时：

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

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

它会挂起一段时间，最终返回：

 did_send = FALSE;

但是如果我使用虚假网址执行异步请求：

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

我

did_send = TRUE;

每次都会得到：。我需要让异步请求正常工作，因为我能够设置超时，而不必在请求超时且默认超时持续时间（异步请求无法更改）时挂起 60 秒。有什么想法吗？

Answer 1

尝试使用 nsurlconnection 类委托方法 connection:didFailWithError: 这应该会为您提供一致的结果。

-(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 不会执行任何操作。它创建该类的一个实例，但不开始数据传输——即使请求无法满足，该对象通常也将是非零。

相反，您的委托对象（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，这会将其调度到执行线程的运行循环上。

有关 NSURLConnectionDelegate 协议的更多信息（包括有关回调中执行的操作的信息），请参阅 Apple 的“URL 加载系统编程指南。"