一、NSURLConnection

NSURLConnection常见的发送请求方法有以下几种

• 同步请求

+ (NSData *)sendSynchronousRequest:(NSURLRequest *)request returningResponse:(NSURLResponse **)response error:(NSError **)error;

• 异步请求：根据对服务器返回数据的处理方式的不同，又可以分为2种
  • block回调

      + (void)sendAsynchronousRequest:(NSURLRequest*) request                          queue:(NSOperationQueue*) queue                                                  completionHandler:(void (^)(NSURLResponse* response, NSData* data, NSError* connectionError)) handler;
    

  • 代理
    成为NSURLConnection的代理，需要遵守NSURLConnectionDataDelegate协议

     - (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate;
     + (NSURLConnection*)connectionWithRequest:(NSURLRequest *)request delegate:(id)delegate;
     //在startImmediately = NO的情况下，需要调用start方法开始发送请求
     - (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:(BOOL)startImmediately;
    

    NSURLConnectionDataDelegate协议中的代理方法

    //  开始接收到服务器的响应时调用
    - (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response;
    //接收到服务器返回的数据时调用（服务器返回的数据比较大时会调用多次）
    - (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data;
    //服务器返回的数据完全接收完毕后调用
    - (void)connectionDidFinishLoading:(NSURLConnection *)connection;
    //请求出错时调用（比如请求超时）
    - (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error;
    

NSMutableURLRequest是NSURLRequest的子类，常用方法有

//设置请求超时等待时间（超过这个时间就算超时，请求失败）
- (void)setTimeoutInterval:(NSTimeInterval)seconds;
//设置请求方法（比如GET和POST）
- (void)setHTTPMethod:(NSString *)method;
//设置请求体
- (void)setHTTPBody:(NSData *)data;
//设置请求头
- (void)setValue:(NSString *)value forHTTPHeaderField:(NSString *)field;