Question 88815 in Flutter Question posted in
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Flutter: The operator '[]' isn't defined for the type 'Future<Map<dynamic, dynamic>>

I’m coding the class

class _DashboardState extends State
with SingleTickerProviderStateMixin {
late Future _summaryData;
late Future<List> _chartData;

  @override
  initState() {
    super.initState();
    Future<Map> data = fetchData();
    _summaryData= data['summaryData']; // ERROR HERE
    _chartData= data['chartData']; // ERROR HERE
  }

  Future<Map> fetchData() async {
    ...
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: _summaryData,
      builder: ...);
  }

but I face an error The operator '[]' isn't defined for the type 'Future<Map<dynamic, dynamic>>'. Try defining the operator '[]'..

Please tell me the reason and how to solve? thank you!

Tags:

2

Answers


  1. 0

    The issue here is that you are trying to access summaryData and chartData from a Future<Map> and not a Map. In your fetchData() function, make it so that you return Map and not a Future<Map> like so:

    Map fetchData() async {
 return await fetchDataAPICall(); /// Whatever way you are fetching the data
}

    This should return you a Map within which you should be able to access your required data.

    Happy Coding 🙂

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  2. 0

    change your code to the following.

      @override
  initState() {
    super.initState();
    getData();
  }

void getData()async{
Future<Map> data = await fetchData();
    _summaryData= data['summaryData']; // ERROR FIX
    _chartData= data['chartData']; // ERROR FIX
}

  Future<Map> fetchData() async {
    ...
  }

  @override
  Widget build(BuildContext context) {
    return FutureBuilder(
      future: _summaryData,
      builder: ...);
  }

    since await cannot be added to init method we create a separate method and mark it async to wait for the api call data.

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