74 NSURLConnection的基本使用

1>NSURLConnection的基本使用：
NSURLConnection常见的发送请求方法有以下几种:

1)同步请求:

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

2)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:

- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate;
+ (NSURLConnection*)connectionWithRequest:(NSURLRequest *)request delegate:(id)delegate;
- (id)initWithRequest:(NSURLRequest *)request delegate:(id)delegate startImmediately:(BOOL)startImmediately;

在startImmediately = NO的情况下，需要调用start方法开始发送请求(其他两种不需要手动start)
- (void)start;

成为NSURLConnection的代理，最好遵守NSURLConnectionDataDelegate协议:
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;