Iphone开发-NSRULRequest，及NSTRLConnection概述：

 HUD = [MBProgressHUD showHUDAddedTo:self.view animated:YES];
        HUD.labelText = @"Load Web Server";
        //HUD.delegate = self;
        NSURL *url = [NSURL URLWithString:@"http://www.facebook.com"];
        NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL: url];
        [request setTimeoutInterval:5];
        NSLog(@"request1::%d",[request timeoutInterval]);
        //NSHTTPURLResponse *response;
        NSURLConnection *connnection = [[NSURLConnection alloc]initWithRequest:request delegate:self];
        CFRunLoopRun();
        //[connnection scheduleInRunLoop:[NSRunLoop currentRunLoop] forMode:NSDefaultRunLoopMode];
        NSLog(@"request2::%d",[request timeoutInterval]);
        [connnection release];

// 异步访问时则要实现委托的一个方法
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response {
        
        // 注意这里将NSURLResponse对象转换成NSHTTPURLResponse对象才能去
        NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)response;
        if ([response respondsToSelector:@selector(allHeaderFields)]) {
                NSDictionary *dictionary = [httpResponse allHeaderFields];
                NSLog(@"%@",[dictionary description]);
                NSLog(@"%d",[httpResponse statusCode]);
                
        }
}
- (void)connectionDidFinishLoading:(NSURLConnection *)connection {
        
 finished = TRUE;
        if (HUD) {
                [HUD removeFromSuperview];
                
                
        }
        [self.view setNeedsDisplay];
}
- (void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error{
        if (HUD) {
                [HUD removeFromSuperview];
                
        }
        UIAlertView *alert = [[UIAlertView alloc]initWithTitle:@"ERROR" message:[error localizedDescription] delegate:nil cancelButtonTitle:@"OK" otherButtonTitles:nil];
        [alert show];
        [alert release];
        

 

NSConnection概述：
}

1、NSURLConnection类的作用是异步下载url请求的内容。因此，在使用此类时，没必要在开一个线程来处理。

2、当其检测到所指向的url要重定向到一个新地址时，它的delegate会接到消息“connection:willSendRequest:redirectResponse: ”，

　　在这个消息处理函数中，你可以允许重定向或指定其它url，也可以拒绝重定向。

3、它有一个简易的类方法“sendSynchronousRequest:returningResponse:error:”，可以用来同步载入url请求的内容。

 

 

异步请求

NSMutableData* buf = [[NSMutableData alloc] initWithLength:0];
NSURLConnection* connection = [[NSURLConnection alloc] initWithRequest:req delegate:self];
 
// 收到响应时, 会触发
- (void)connection:(NSURLConnection *)aConnection didReceiveResponse:(NSURLResponse *)aResponse;
// 你可以在里面判断返回结果, 或者处理返回的http头中的信息
 
// 每收到一次数据, 会调用一次
- (void)connection:(NSURLConnection *)aConn didReceiveData:(NSData *)data;
// 因此一般来说,是
- (void)connection:(NSURLConnection *)aConn didReceiveData:(NSData *)data
{
    [buf appendData:data];
}
// 当然buffer就是前面initWithRequest时同时声明的.
 
// 网络错误时触发
- (void)connection:(NSURLConnection *)aConn didFailWithError:(NSError *)error;
 
// 全部数据接收完毕时触发
- (void)connectionDidFinishLoading:(NSURLConnection *)aConn;

同步請求
// 初始化請求 NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init]; // 設置URL

[request setURL:[NSURL URLWithString:urlStr]];
// 設置HTTP方法
        [request setHTTPMethod:@"GET"];
// 發送同步請求, 這裡得returnData就是返回得數據楽
        NSData *returnData = [NSURLConnection sendSynchronousRequest:request 
                                                   returningResponse:nil error:nil]; 
// 釋放對象
        [request release];