Dart, Flutter - I change data in MapList at index 0 But data in MapList index 1 also change it-CodePudding

This is my data map list

data =
[
  {
    "group": "A",
    "direction": "N",
    "city": [
      {
        "city": "CITY1",
        "code": "001",
        "subCity": [
          {
            "subCityCode": "C1001",
            "member": "15"
          },
          {
            "subCityCode": "C1002",
            "member": "20"
          }
        ]
      },
      {
        "city": "CITY2",
        "code": "002",
        "subCity": [
          {
            "subCityCode": "C2001",
            "member": "42"
          },
          {
            "subCityCode": "C2002",
            "member": "65"
          }
        ]
      },
    ]
  },
  {
    "group": "B",
    "direction": "S",
    "city": [
      {
        "city": "CITY1",
        "code": "001",
        "subCity": [
          {
            "subCityCode": "C1001",
            "member": "21"
          }
          {
            "subCityCode": "C1002",
            "member": "47"
          }
        ]
      },
      {
        "city": "CITY2",
        "code": "002",
        "subCity": [
          {
            "subCityCode": "C2001",
            "member": "65"
          }
          {
            "subCityCode": "C2002",
            "member": "17"
          }
        ]
      },
    ]
  },
]

I would like to change "member": "100" of "subCityCode": "C1001" of "city": "CITY1" of "group": "A"

Therefore I write code like this

data[0]['city'][0]['subCity'][0]['member'] = 100;

And the result is

data =
[
  {
    "group": "A",
    "direction": "N",
    "city": [
      {
        "city": "CITY1",
        "code": "001",
        "subCity": [
          {
            "subCityCode": "C1001",
            "member": "100"
          },
          {
            "subCityCode": "C1002",
            "member": "20"
          }
        ]
      },
      {
        "city": "CITY2",
        "code": "002",
        "subCity": [
          {
            "subCityCode": "C2001",
            "member": "42"
          },
          {
            "subCityCode": "C2002",
            "member": "65"
          }
        ]
      },
    ]
  },
  {
    "group": "B",
    "direction": "S",
    "city": [
      {
        "city": "CITY1",
        "code": "001",
        "subCity": [
          {
            "subCityCode": "C1001",
            "member": "100"
          }
          {
            "subCityCode": "C1002",
            "member": "47"
          }
        ]
      },
      {
        "city": "CITY2",
        "code": "002",
        "subCity": [
          {
            "subCityCode": "C2001",
            "member": "65"
          }
          {
            "subCityCode": "C2002",
            "member": "17"
          }
        ]
      },
    ]
  },
]

why the data at index 1 also change it

Why data[1] at ['city'][0] at ['subCity'][0] at ['member'] = 100

and how to change only data[0]

--Thank you--

CodePudding user response：

I suppose you have added this data by code, and since dart works on refrences the 2nd object has the same refrence as the first one (as i can see the values are the same)

You can try jsonDecode jsonEncode on object before adding to map.

I have tried the same code and it works fine

void main() {
  var data =
  [
    {
      "group": "A",
      "direction": "N",
      "city": [
        {
          "city": "CITY1",
          "code": "001",
          "subCity": [
            {
              "subCityCode": "C1001",
              "member": "15"
            },
            {
              "subCityCode": "C1002",
              "member": "20"
            }
          ]
        },
        {
          "city": "CITY2",
          "code": "002",
          "subCity": [
            {
              "subCityCode": "C2001",
              "member": "42"
            },
            {
              "subCityCode": "C2002",
              "member": "65"
            }
          ]
        },
      ]
    },
    {
      "group": "B",
      "direction": "S",
      "city": [
        {
          "city": "CITY1",
          "code": "001",
          "subCity": [
            {
              "subCityCode": "C1001",
              "member": "21"
            },
            {
              "subCityCode": "C1002",
              "member": "47"
            }
          ]
        },
        {
          "city": "CITY2",
          "code": "002",
          "subCity": [
            {
              "subCityCode": "C2001",
              "member": "65"
            },
            {
              "subCityCode": "C2002",
              "member": "17"
            }
          ]
        },
      ]
    },
  ];

  (data[0]['city'] as List)[0]['subCity'][0]['member'] = "100";

  print("NEW DATA --- ${data}");
}