同步 和 异步网络请求

//同步请求可以一次性的接收所有数据  但是在主线程中完成  会阻塞主线程

-(void)sendRequestTongbu

{

    //创建一个NSSring类型的URL连接字符串

    NSString *urlString = @"http://www.apple.com";

    //转换成NSURL类型

    NSURL *url = [NSURL URLWithString:urlString];

    //实例化一个request，把URL对象赋值到NSURLRequest对象中

    NSURLRequest *request = [NSURLRequest requestWithURL:url];

    NSError *error = nil;

    //获得数据

    NSData *data = [NSURLConnectionsendSynchronousRequest:request returningResponse:nilerror:&error];

    

    //在下载完数据后，一般都需要做data是否为空的判断

    if (data == nil)

    {

        NSLog(@"send request failed");

        return;

        

    }

    NSString *str = [[NSStringalloc] initWithData:data encoding:NSUTF8StringEncoding];

    NSLog(@"%@",str);

}

//异步请求  需要在代理中接收数据  不会阻塞当前线程 记得加上<NSURLConnectionDataDelegate>

-(void)senderRequestYibu

{

    NSString *urlString = @"http://www.cnblogs.com/chenhaosuibi/";

    NSURL *url = [NSURL URLWithString:urlString];

    NSURLRequest *resquest = [NSURLRequest requestWithURL:url];

    

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

    

    if (connection) {

        NSLog(@"链接成功");

    }

    else

        

    {

        NSLog(@"链接失败");

    }

}

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

{

    NSLog(@"收到响应，请求成功");

    NSLog(@"%@",response);

    // 可以在里面判断返回结果, 或者处理返回的http头中的信息

}

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

{

    NSLog(@"收到了Data");

    NSString *dataStr = [[NSStringalloc] initWithData:data encoding:NSUTF8StringEncoding];

    NSLog(@"dataStr = %@",dataStr);

}

- (void)connectionDidFinishLoading:(NSURLConnection *)connection

{

    NSLog(@"全部接受完数据后触发");

}

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

{

    NSLog(@"链接出错");

    NSLog(@"%@",error);

}