异步GET请求（使用委托）

- (void)getRegions

{

    NSURL *url = [[NSURL alloc] initWithString:urlString];

    

    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10];

    [request setHTTPMethod:@"GET"];

    [request setValue:@"value" forHTTPHeaderField:@"请求头"];

    //NSData *received = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:nil];

    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request delegate:self];

    if (connection)

    {

        self.datas = [NSMutableData new];

    }

//    NSError *error;

//    NSDictionary *jsonDic = [NSJSONSerialization JSONObjectWithData:received options:kNilOptions error:&error];

//    return jsonDic;

}

#pragma mark- NSURLConnection 回调方法

- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

{// ①

    [_datas appendData:data];

}

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

{

    NSLog(@"%@",[error localizedDescription]);

}

- (void) connectionDidFinishLoading: (NSURLConnection*) connection

{//         ②

    NSLog(@"请求完成…");

    NSDictionary* dict = [NSJSONSerialization JSONObjectWithData:_datas options:NSJSONReadingAllowFragments error:nil];

    //[self reloadView:dict];

    NSLog(@"%@", dict);

}