how can i make DropdownMenuItem accept any type-CodePudding

i have the follwing ListView.builder

List fieldName = [
{
 'name':Alex,
  'values' [1,2,3,4],
},
{
 'name':jack,
  'values' ['jack','samer'],
}
]
ListView.builder(
itemCount: fieldName.length,
itemBuilder: (BuildContext context, int index) {
 return  DropdownButtonFormField(
  onChanged: (theLang) {},
   items: fieldName[index]['values']
   .map<DropdownMenuItem<String>>(( String value){
    return DropdownMenuItem(
     value: value,
       child: Text (value),
      );
   }).toList()
 );
)

error message type '(String) => DropdownMenuItem' is not a subtype of type '(int) => DropdownMenuItem' of 'f'

i know this because the int list .. but how could i make it work .. the list values comes from server .. sometimes int sometimes strings

i tried to remove the type name in

.map((value){.... but still no hope

CodePudding user response：

Here you have indicated that the DropdownMenuItem will handle value of type String by including the type like this DropdownMenuItem<String>

Just use it without the datatype like this,

return  DropdownButtonFormField(
           items: ['A', 1].map(
              (value) => 
              DropdownMenuItem(
                value: value,
                child: Text('$value'),),).toList(),
           onChanged: (x) {},
        );

also dont forget to use String interpolation while using the value in Text() widget

CodePudding user response：

The value field just call toString() like the code below.

import 'package:flutter/material.dart';

class Test extends StatelessWidget {
  const Test({Key? key}) : super(key: key);

  @override
  Widget build(BuildContext context) {
    const fieldName = [
      {
        'name': "Alex",
        'values': [1, 2, 3, 4],
      },
      {
        'name': "jack",
        'values': ['jack', 'samer'],
      }
    ];

    return SizedBox(
      height: 200,
      child: ListView.builder(
          itemCount: fieldName.length,
          itemBuilder: (BuildContext context, int index) {
            return DropdownButtonFormField(
                onChanged: (theLang) {},
                items: (fieldName[index]['values'] as List)
                    .map<DropdownMenuItem<String>>((value) {
                  return DropdownMenuItem(
                    value: value.toString(),
                    child: Text(value.toString()),
                  );
                }).toList());
          }),
    );
  }
}