序列化与反序列化

序列化[把OC对象序列化为有特殊格式的字符串]
用类NSJSONSerialization可以对oc和josn对象进行转换

    NSDictionary *dict = @{
                           @"name":@"xiaomage",
                           @"age" :@18
                           };
    
    NSArray *arrM = @[@"123",@"456"];
    NSString *str = @"xiaomage";
    
    /*
     - Top level object is an NSArray or NSDictionary
      顶层必须是字典或者是数组
     - All objects are NSString, NSNumber, NSArray, NSDictionary, or NSNull
     - All dictionary keys are NSStrings
     - NSNumbers are not NaN or infinity
     null ----- NSNull
     */
    BOOL isValid = [NSJSONSerialization isValidJSONObject:str];
    if (isValid) {
        //OC---->jsoN
        //NSJSONWritingPrettyPrinted 排版
        NSData *data = [NSJSONSerialization dataWithJSONObject:str options:NSJSONWritingPrettyPrinted error:nil];
        
        NSString *result = [[NSString alloc]initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@\n%@",result,arrM);

    }else
    {
        NSLog(@"不能转换");
    }

反序列化[把JSON字符串反序列化为OC的对象]

//1.确定请求路径
    NSURL *url = [NSURL URLWithString:@"http://120.25.226.186:32812/login?username=123&pwd=abc&type=JSON"];
    
    //2.创建请求对象uc
    NSURLRequest *request = [NSURLRequest requestWithURL:url];
    
    //3.发送GET请求
    [NSURLConnection sendAsynchronousRequest:request queue:[NSOperationQueue mainQueue] completionHandler:^(NSURLResponse * _Nullable response, NSData * _Nullable data, NSError * _Nullable connectionError) {
        
        //{"error":"用户名不存在"}
        // "error"
        
        //4.解析数据
        /*
         第一个参数:要解析的二进制数据(json)
         第二个参数:
         NSJSONReadingMutableContainers = (1UL << 0), 表示时一个可变的数组或者是字典
         NSJSONReadingMutableLeaves = (1UL << 1),     字符串也是可变   iOS7有问题
         NSJSONReadingAllowFragments = (1UL << 2)     既不是数组也不是字典,必须使用该枚举值
         第三个参数:错误信息
         */
        NSDictionary *dict =  [NSJSONSerialization JSONObjectWithData:data options:kNilOptions error:nil];
        NSLog(@"%@",dict[@"error"]);
        
    }];