维护 NSMutableDictionary 元素的顺序 [重复]

Question

我得到了以下格式的字典：

[
  {
    "position": "1",
    "name": "Jaen",
    "group": "Student",
    "Address": "Delhi"
  },
  {
    "position": "2",
    "name": "Jaen",
    "group": "Student",
    "Address": "Delhi"
  },
  {
    "position": "1",
    "name": "Jaen",
    "group": "Teacher",
    "Address": "Delhi"
  }
]

基本上，我想围绕名为“group”的键对它们进行分组。我必须创建一个以下格式的字典来在我的 UI 中填充数据。

[
  {
    "Student": [
      {
        "position": "1",
        "name": "Jaen",
        "group": "Student",
        "Address": "Delhi"
      },
      {
        "position": "2",
        "name": "Jaen",
        "group": "Student",
        "Address": "Delhi"
      }
    ],
    "Teacher": [
      {
        "position": "1",
        "name": "Jaen",
        "group": "Teacher",
        "Address": "Delhi"
      }
    ]
  }
]

应该保持小组的顺序，即学生应该在老师之前。但是当我打印 dictGroupField 时，它会根据顺序给出随机结果。

我怎样才能维持秩序？

请在下面找到我正在使用的代码：

    @property (strong, nonatomic) NSMutableDictionary *dictGroupField;


    -(void)loadFieldData {

    _dictGroupField = [[NSMutableDictionary alloc] init];  

     NSMutableArray *arrayFields = [self getArrayFields];

          for (NSDictionary *dictT in arrayFields) {
    NSString *strGroup = [dict valueForKey:@"group"];

    if ([_dictGroupField valueForKey:strGroup] == nil) {

                    NSMutableArray *arrGroup = [[NSMutableArray alloc] init];
                    [arrGroup addObject:dict];
                    [_dictGroupField setObject:arrGroup forKey:strGroup];
                } else {
                    NSMutableArray *arrGroupExist = [_dictGroupField valueForKey:strGroup];
                    [arrGroupExist addObject:dict];
                    [_dictGroupField setObject:arrGroupExist forKey:strGroup];
                }
    }

}

Answer 1

你无法维持它的秩序。
字典是键值关联的无序集合。查看更多Docs