[iOS] HTTP請求方法

如下：

#pragma mark 同步GET方式下載圖片 downPath爲圖片路徑
- (void)downloadFileSync: (NSString *)downPath{
    //建立URL對象
    NSURL *url = [NSURL URLWithString:downPath];
    //建立請求對象
    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0f];
    NSURLResponse *responseData = nil;//應答數據
    NSError *err = nil;//錯誤記錄
    //發送網絡同步請求獲取遠程數據
    NSData *imageData = [NSURLConnection sendSynchronousRequest:request returningResponse:&responseData error:&err];
    NSLog(@"responseData: %@", responseData);
    if (err) {
        NSLog(@"err: %@", err);
        return;
    }
    //從網絡應答生成圖片，並顯示在imageView中
//    self.imageToDisp.image = [UIImage imageWithData:imageData];
    
    return;
}

服務器返回的responseData爲：

<NSHTTPURLResponse: 0x7fba496e3a80> 

{ URL: http://edutohome-upload.stor.sinaapp.com/1433834502upload.png } 

{ status code: 200, headers {

    "Accept-Ranges" = bytes;

    "Cache-Control" = "max-age=7200";

    Connection = "keep-alive";

    "Content-Length" = 43546;

    "Content-Type" = "image/png";

    Date = "Tue, 09 Jun 2015 07:21:42 GMT";

    Etag = 1db5335d9e6fef747fc9d35f78fe3c67;

    Expires = "Tue, 09 Jun 2015 09:21:42 GMT";

    "Last-Modified" = "Tue, 09 Jun 2015 07:21:42 GMT";

    Server = "nginx/1.4.4";

    "X-Sws-Timestamp" = "1433834502.42126";

    "X-Trans-Id" = "tx5eb26269aa334a36a1153-0055769406";

} }

---

異步方式下載須要使用NSURLConnectionDataDelegate委託方法，分爲幾步：

1. 發送異步鏈接請求

2. 完成回調函數－(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response

3. 完成回調函數-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data

4. 完成回調函數-(void)connectionDidFinishLoading:(NSURLConnection *)connection

#pragma mark 異步GET方式下載
- (IBAction)downMusic:(NSString *)downPath {
    //建立URL對象
    NSURL *url = [NSURL URLWithString:downPath];
    //建立請求對象
    NSURLRequest *request = [NSURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10.0f];
    //發送異步鏈接請求
    [NSURLConnection connectionWithRequest:request delegate:self];
}

#pragma mark 得到服務器響應後調用該方法，僅調用一次
-(void)connection:(NSURLConnection *)connection didReceiveResponse:(NSURLResponse *)response{
    //建立存放圖片文件的對象
//    self.data = [NSMutableData new];
    //獲取mp3文件大小
//    self.lenght = [response expectedContentLength];
}

#pragma mark 接受到應答數據以後調用，會被屢次調用
-(void)connection:(NSURLConnection *)connection didReceiveData:(NSData *)data{
    //追加每次返回的數據至存放對象
//    [self.data appendData:data];
//    self.curLenght = [self.data length];
}

#pragma mark 接收完成數據時調用
-(void)connectionDidFinishLoading:(NSURLConnection *)connection{
    //顯示／保存圖片
}

另外一種HTTP異步請求方式，採用POST，REST/JSON風格，並設置了Header和Body

    NSURL *url = [NSURL URLWithString: [NSString stringWithFormat:@"%@", @"http://localhost:8080/register"]];
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:3.0];
    //設置POST方式
    [request setHTTPMethod:@"POST"];
    //設置Header: content-type
    [request setValue:@"application/json" forHTTPHeaderField:@"content-type"];
    //設置Body
    NSDictionary *dict = @{@"name":@"Suares"};
    [request setHTTPBody:nsData];
    
    //異步代碼塊方式
    [NSURLConnection sendAsynchronousRequest:request queue:[[NSOperationQueue alloc]init] completionHandler:^(NSURLResponse *response, NSData *data, NSError *connectionError) {
        NSLog(@"執行代碼塊");
        NSDictionary *dictResp = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingAllowFragments error:nil];
        NSArray *dictItems = dictResp[@"items"];
        NSString *status = dictResp[@"status"];
        NSString *name = dictItems[0][@"name"];
        //處理接收的數據,(注意在主線程中更新UI)
        dispatch_async(dispatch_get_main_queue(), ^{
            self.myText.text = [NSString stringWithFormat:@"%@\n%@", status, name];
        });
        
        NSLog(@"請求完成！");