IOS之同步请求、异步请求、GET请求、POST请求(2)

3、异步GET请求
    //第一步，创建url
    NSURL *url = [NSURL URLWithString:@"http://api.hudong.com/iphonexml.do?type=focus-c"];
    //第二步，创建请求
    NSURLRequest *request = [[NSURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10];
    //第三步，连接服务器
    NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];

4、异步POST请求
    //第一步，创建url
    NSURL *url = [NSURL URLWithString:@"http://api.hudong.com/iphonexml.do"];
    //第二步，创建请求
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc]initWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10];
    [request setHTTPMethod:@"POST"];
    NSString *str = @"type=focus-c";
    NSData *data = [str dataUsingEncoding:NSUTF8StringEncoding];
    [request setHTTPBody:data];
    //第三步，连接服务器
    NSURLConnection *connection = [[NSURLConnection alloc]initWithRequest:request delegate:self];

5、异步请求的代理方法
//接收到服务器回应的时候调用此方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{
    NSHTTPURLResponse *res = (NSHTTPURLResponse *)response;
    NSLog(@"%@",[res allHeaderFields]);
    self.receiveData = [NSMutableData data];
 

                             
}
//接收到服务器传输数据的时候调用，此方法根据数据大小执行若干次
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data
{
    [self.receiveData appendData:data];
}
//数据传完之后调用此方法
-(void)connectionDidFinishLoading:(NSURLConnection *)connection
{
    NSString *receiveStr = [[NSString alloc]initWithData:self.receiveData encoding:NSUTF8StringEncoding];
    NSLog(@"%@",receiveStr);
}
//网络请求过程中，出现任何错误（断网，连接超时等）会进入此方法
-(void)connection:(NSURLConnection *)connection
 didFailWithError:(NSError *)error
{
    NSLog(@"%@",[error localizedDescription]);
}