NSJSONSerialization

NSJSONSerialization是系统自带的解析JSON数据的类。

NSDictionary --> JSON

    NSDictionary *dic = @{
                          @"time"   : @"2018-04-03",
                          @"item"   : @"NSJSONSerialization",
                          @"data"   : @{
                                        @"info": @"12"
                                        }
                          };
    NSString *filePath = NSSearchPathForDirectoriesInDomains(NSLibraryDirectory, NSUserDomainMask, YES).firstObject;
    filePath = [filePath stringByAppendingPathComponent:@"dic"];
    
    /*  NSJSONWritingOptions  枚举
     *  NSJSONWritingPrettyPrinted  将JSON数据格式化，可读性高
     *  NSJSONWritingSortedKeys     不做任何操作，返回一串字符串
     */
    
    NSError *error;
    NSData *data = [NSJSONSerialization dataWithJSONObject:dic options:NSJSONWritingPrettyPrinted error:&error];
    if (error){
        NSLog(@"object to json data error");
        return;
    }else {
        NSString *string = [[NSString alloc] initWithData:data encoding:NSUTF8StringEncoding];
        NSLog(@"%@",string);
    }
        
       /* NSJSONWritingPrettyPrinted 输出
         {
           "data" : {
                      "info" : "12"
                    },
           "time" : "2018-04-03",
           "item" : "NSJSONSerialization"
         }
         */
        
        // NSJSONWritingSortedKeys  输出  {"data":{"info":"12"},"item":"NSJSONSerialization","time":"2018-04-03"}
    

JSON --> NSDictionary

    /*  NSJSONReadingOptions 枚举
     *  NSJSONReadingMutableContainers 返回的是可变容器
     *  NSJSONReadingMutableLeaves     返回的内部的值可变对象
     *  NSJSONReadingAllowFragments    允许返回最外层既不是NSArray也不是NSDictionary，但必须是有效的JSON Fragment.
     */
    NSDictionary *dic = [NSJSONSerialization JSONObjectWithData:data options:NSJSONReadingMutableContainers error:&error];
    if (error) {
        NSLog(@"json data to object error");
        return;
    }