iOS使用NSURLConnection發送同步和異步HTTP Request

1. 同步發送

- (NSString *)sendRequestSync
{
    // 初始化請求, 這里是變長的, 方便擴展
    NSMutableURLRequest *request = [[NSMutableURLRequest alloc] init];

    // 設置
    [request setURL:[NSURL URLWithString:urlStr]];
    [request setHTTPMethod:@"POST"];
    [request setValue:host forHTTPHeaderField:@"Host"];
    NSString *contentLength = [NSString stringWithFormat:@"%d", [content length]];
    [request setValue:contentLength forHTTPHeaderField:@"Content-Length"];
    [request setHTTPBody:content];

    // 發送同步請求, data就是返回的數據
    NSError *error = nil;
    NSData *data = [NSURLConnection sendSynchronousRequest:request returningResponse:nil error:&error];
    if (data == nil) {
        NSLog(@"send request failed: %@", error);
        return nil;
    }

    NSString *response = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
    NSLog(@"response: %@", response);
    return response;
}

2.異步發送

1) 使用delegate的方式:

 

- (void)sendRequestAsync
{
    // 初始化請求
    NSMutableURLRequest  *request = [[NSMutableURLRequest alloc] init];

    // 設置
    [request setURL:[NSURL URLWithString:urlStr]];
    [request setCachePolicy:NSURLRequestUseProtocolCachePolicy]; // 設置緩存策略
    [request setTimeoutInterval:5.0]; // 設置超時

    //......

    receivedData = [[NSMutableData alloc] initData: nil];

    NSURLConnection *connection = [[NSURLConnection alloc] initWithRequest:request     delegate:self];
    if (connection == nil) {
        // 創建失敗
        return;
    }
}

異步發送使用代理的方式, 需要實現以下delegate接口:

// 收到回應
- (void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response
{    
    NSLog(@"receive the response");
    // 注意這里將NSURLResponse對象轉換成NSHTTPURLResponse對象才能去
    NSHTTPURLResponse *httpResponse = (NSHTTPURLResponse*)response;
    if ([response respondsToSelector:@selector(allHeaderFields)]) {
        NSDictionary *dictionary = [httpResponse allHeaderFields];
        NSLog(@"allHeaderFields: %@",dictionary);
    }
    [receivedData setLength:0];
}    

// 接收數據   
- (void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data    
{
    NSLog(@"get some data");
    [receivedData appendData:data];    
}

// 數據接收完畢
- (void)connectionDidFinishLoading:(NSURLConnection *)connection    
{
    NSString *results = [[NSString alloc]
                         initWithBytes:[receivedData bytes]
                         length:[receivedData length]
                         encoding:NSUTF8StringEncoding];

    NSLog(@"connectionDidFinishLoading: %@",results);
}
 
// 返回錯誤
-(void)connection:(NSURLConnection *)connection didFailWithError:(NSError *)error    
{   
    NSLog(@"Connection failed: %@", error);        
}    

2) iOS 5.0版本新增異步發送接口:

+ (void)sendAsynchronousRequest:(NSURLRequest *)request
                          queue:(NSOperationQueue*) queue
              completionHandler:(void (^)(NSURLResponse*, NSData*, NSError*)) handlerNS_AVAILABLE(10_7, 5_0);