我正在使用NSURLConnection发送HTTP请求，并使用[[NSURLConnection alloc]initWithRequest:request delegate:self]运行它；其中“request”是已配置的NSMutableURLRequest对象。如果出现基于错误代码（404或500）的HTTP错误，我想重试该请求。

我得到了错误响应和HTTP状态代码中的"连接： didReceiveContent"委托方法。我应该如何实现重试请求？

提前感谢！

附言：我试图取消连接并在收到错误时启动它，但没有效果，因为NSURLConnection在完成加载或被取消后释放委托。

-----更新-----

    -(void)doHTTPGet:(NSString *)url delegate:(id  <NSURLConnectionDelegate>)delegate timeout:(NSTimeInterval)timeout
{
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:[NSURL URLWithString:url]
                                                           cachePolicy:NSURLRequestUseProtocolCachePolicy
                                                       timeoutInterval:timeout];
    [request setHTTPMethod:@"GET"];
    [request setValue:@"application/x-www-form-urlencoded" forHTTPHeaderField:@"Content-Type"];

    // send request by instanciating NSURLConnection
    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:delegate];

}

在我的模型类中，我有调用方方法和委托

来电者：

[MyModel doHTTPGet:url delegate:self timeout:HTTP_TIMEOUT];

委托方法：

- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse *)response;
    httpResponseStatusCode = [httpResponse statusCode];
    DLOG(@"HTTP status code=%ld", (long)httpResponseStatusCode);

    if (httpResponseStatusCode == 404)
    {
       // RETRY HERE
    } 
}

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [httpResponseData appendData:data];
}

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

    // some code PROCESSING RESPONSE
}

- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error {
        }