图片下载

NSString *api = @"http://i2.cqnews.net/car/attachement/jpg/site82/20120817/5404a6b61e3c1197fb211d.jpg";
NSURLSessionDataTask *dataTask =  [[NSURLSession sharedSession]dataTaskWithURL:[NSURL URLWithString:api] completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        
        NSLog(@"response:%@",response);
        UIImage *image = [UIImage imageWithData:data];
        NSLog(@"error:%@",error);
    }];

歌曲下载

{
    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration ephemeralSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    NSURLSessionDataTask *task = [_session dataTaskWithRequest:mutiRequest];
    [task resume];
}
//第一步: 接受响应
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler{

    NSHTTPURLResponse *resp = (NSHTTPURLResponse*)response;
    //文件总大小
    NSLog(@"%lld",resp.expectedContentLength);
    NSLog(@"--->%@",response);
    
    if(resp.statusCode == 200){
    
        completionHandler(NSURLSessionResponseAllow);
    }
}
//第二步: 接受数据
- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask
    didReceiveData:(NSData *)data{


    NSLog(@"-->%ld",data.length);
    [_datas appendData:data];
｝
//第三步: 下载完成
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task
didCompleteWithError:(nullable NSError *)error{

    if(!error){
        NSLog(@"done");
    ｝
    else {
        NSLog(@"error: %@", error);
    }
｝