The argument type 'List<Set<Card>>' can't be assigned to the parameter type 'List<Widget>'

user_2015609 0
Viewed 222

Flutter shows me the following error message although I converted map into List

The argument type 'List<Set<Card>>' can't be assigned to the parameter type 'List<Widget>'.dartargument_type_not_assignable

May you please tell me what's wrong?

class MyHomePage extends StatelessWidget {
  MyHomePage({Key? key, required String title}) : super(key: key);

  final List<Transaction> transactions = [
    Transaction(
        id: 'sh1', 
        date: DateTime.now(), 
        title: 'School', 
        value: 1554.5
        ),
    Transaction(
      id: 'sc5',
      date: DateTime.now(), 
      title: 'Sucar', 
      value: 16.5
      ),
  ];

  @override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: Text("title"),
      ),
      body: Column(
        crossAxisAlignment: CrossAxisAlignment.stretch,
        children: [
          const Card(
            color: Color.fromRGBO(200, 165, 245, 1.0),
            child: Text('[CHART]'),
          ),
          Column(
            children:
/////// ERROR
              transactions.map( (e) => { return Card(child: Text(e.title),); } ).toList(),
          ),
        ],
      ),
    );
  }
}
dart flutter
2 Answers

This:

transactions.map( (e) => { return Card(child: Text(e.title),); } ).toList(),

should probably be

transactions.map((e) => Card(child: Text(e.title))).toList(),

or if you prefer the long form:

transactions.map((e) { return Card(child: Text(e.title),); } ).toList(),

But you cannot mix them, otherwise the compiler will interpret the superfluous {} as an intent to have a Set<> of your items returned instead of a single one.

user_20607250

Dont use => and return togenther. => is a shorthand for return and it doenst need curly braces {} to define the method boundary.

transactions.map((e) => Card(child: Text(e.title))).toList(),

This is the preferred way.

user_134558350
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