• 1.同步请求，一旦发送请求，程序禁止用户交互，直到服务器返回数据完成，才能进行下一步操作
  • 2.异步请求不会阻塞主线程，而回建立一个新的线程来操作，用户发出请求以后，可以继续对UI操作，程序可以继续运行
  • 3.GET请求，将参数直接写在访问路径上。操作简单，但是容易被外界看到，安全性不高。
  • 4.POST请求，将参数放到body里面，POST操作相对复杂，需要将参数和地址分开，相对更加安全.

GET请求

    NSString *urlString = KgetUrl;
    NSURL *url = [NSURL URLWithString:urlString];
    //创建请求体
    NSURLRequest *request = [NSURLRequest  requestWithURL:url];
    
    //创建一个session对象
    NSURLSession *session = [NSURLSession sharedSession];
    
    //创建请求任务
    NSURLSessionTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        
        NSString *result = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        
        NSLog(@"GTE:%@",result);
    }];
    //注意不能忘了这一步
    [task resume];

POST请求

 NSString *urlString = KpostUrl;
    NSURL *url = [NSURL URLWithString:urlString];
    //创建请求体，注意是 NSMutableURLRequest
    NSMutableURLRequest *request = [NSMutableURLRequest requestWithURL:url];
    //设置为POST请求
    [request setHTTPMethod:@"POST"];
    
    NSString *postString = KparameterUrl;
    
    NSData *data = [postString dataUsingEncoding:NSUTF8StringEncoding];
    //添加参数
    [request setHTTPBody:data];
    
    //创建session对象
    NSURLSession *session = [NSURLSession sharedSession];
    
    //创建一个请求任务
    NSURLSessionTask *task = [session dataTaskWithRequest:request completionHandler:^(NSData * _Nullable data, NSURLResponse * _Nullable response, NSError * _Nullable error) {
        NSString *result = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"POST%@",result);
    }];
    
    [task resume];

代理

- (IBAction)delegateAction:(UIButton *)sender {
    
    //遵循代理 <NSURLSessionDataDelegate>
         //
    NSURLSession *session = [NSURLSession sessionWithConfiguration:[NSURLSessionConfiguration defaultSessionConfiguration] delegate:self delegateQueue:[NSOperationQueue mainQueue]];
    //新建任务
    NSURLRequest *request = [NSURLRequest requestWithURL:[NSURL URLWithString:KgetUrl] cachePolicy:NSURLRequestUseProtocolCachePolicy timeoutInterval:10];
    //创建请求
    NSURLSessionDataTask *task = [session dataTaskWithRequest:request];
    
    [task resume];
    
}

- (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveResponse:(NSURLResponse *)response completionHandler:(void (^)(NSURLSessionResponseDisposition))completionHandler{
    
    //当网络基于HTTP协议时,response是NSHTTPURLResponse类型的
//    NSHTTPURLResponse *URLResponse = (NSHTTPURLResponse *)response;
//    long long length = URLResponse.expectedContentLength;
//    NSLog(@"%ld",URLResponse.statusCode);
//    NSLog(@"%lld",length);
    
    //允许服务器回传数据
    completionHandler(NSURLSessionResponseAllow);
}

//接受服务器传回来的数据，可能执行多次
-  (void)URLSession:(NSURLSession *)session dataTask:(NSURLSessionDataTask *)dataTask didReceiveData:(NSData *)data{
    
 
    NSString *string=[[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
    if (string) {
        [self.astring appendString:string];

    }
        NSLog(@"%@",self.astring);


}

//接受或者失败时调用
- (void)URLSession:(NSURLSession *)session task:(NSURLSessionTask *)task didCompleteWithError:(NSError *)error{
    NSLog(@"%@******",error);
    
}

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