1: 使用代理

        //1.delegate

        //创建url

     NSURL *url = [[NSURL alloc] initWithString:@"http:"];

//     创建request

     NSURLRequest *urlRequesr = [[NSURLRequest alloc] initWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:30];

//     发送异步请求

//     异步请求不知道什么时候获取到数据,用delegate这种模式来创建,当获取到数据后,会自动调转到代理方法中

     [NSURLConnection connectionWithRequest:urlRequesr delegate:self];

#pragma mark - NSURLConnectionDataDelegate

    //请求出现错误

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

{

    NSLog(@"%@", error);

}

//- (NSURLRequest *)connection:(NSURLConnection *)connection willSendRequest:(NSURLRequest *)request redirectResponse:(NSURLResponse *)response

//{

//    

//}

    //请求收到回应(可以认为请求开始)

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

{

    NSLog(@"%@", response);

    self.mData = [NSMutableData data];

     

}

    //请求获取到数据

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

{

    NSLog(@"%@", data);

        //网络上的数据以包得形式,一个包一个包得传递过来,需要把收到包数据整合到一起

    [_mData appendData:data];

}

    //请求完成

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

{

    UIImage *image = [UIImage imageWithData:_mData];

    self.view.backgroundColor = [UIColor colorWithPatternImage:image];

}

2: 使用Block

  NSURL *url = [NSURL URLWithString:@""];

    NSURLRequest *urlRequest = [NSURLRequest requestWithURL:url];

    [NSURLConnection sendAsynchronousRequest:urlRequest queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {

        NSLog(@"%@", data);

        self.myData = data;

        [self readData];

    }];

- (void)readData {

    UIImage *image = [[UIImage alloc] initWithData:_myData];

    self.view.backgroundColor = [UIColor colorWithPatternImage:image];

}