iOS 使用NSURLSession进行网络请求

 1.获取session
NSURLSession *session = [NSURLSession sharedSession];
 2.设置url
NSURL *url =
[NSURL URLWithString:[urlStr stringByAddingPercentEncodingWithAllowedCharacters:[NSCharacterSet URLQueryAllowedCharacterSet]]];
 3.创建可变的request
NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
 4.添加参数
NSString *param = [NSString stringWithFormat:@"account=%@&password=%@", name, pwd];
request.HTTPBody = [param dataUsingEncoding:NSUTF8StringEncoding];
 5.设置请求方式为POST
request.HTTPMethod = @"POST";
 6.设置请求头(可选, 在必要时添加)
[request setValue: value forHTTPHeaderField: key];
 7.创建task 并设置请求回调的block
NSURLSessionDataTask *dataTask = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
    if (error) {
        NSLog(@"%@", [error localizedDescription]);
    }
    if (data) {
        NSDictionary *dict = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:nil];
        NSLog(@"%@", dict);
    }
}];
 8.开始请求
[dataTask resume];