DropdownButtonFormField & Validation from API

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Requirements :
– API Service
– Object Model
Developer Recommendation : NB!!! – Use QuickType for your model.
(You need an already working api with a JSON response for quicktype) https://app.quicktype.io/
– DropDownMenuItem
NB!!! – The DropDownMenuItem must be wrapped in a form widget to implement validation.

HINT : Avoid casting variable types such as <String> or <List> or <Object> until your list is actually working. In the DropdownButtonFormField Snippet, you will see no types are declared.

Step 1 :
Configuration :
(On your page.dart or screen.dart)

You need to include these.
1 : Your Model from QuickType

// Model
import './model/support_fields_model.dart';
// API
import 'package:project_name/api/support_fields_service.dart';
// Includes
import 'package:flutter/material.dart';

DropdownButtonFormField Snippet :

child: Form(
  key: globalFormKey,
    Container(
      child: DropdownButtonFormField(
        hint: Text("-- Select Query --"),
        value: querySelect,
        validator: (querySelect) =>
            querySelect ==
                    "-- Select Query --"
                ? 'Select Query Required'
                : null,
        onChanged: (newValue) {
          setState(() {
            dropDownButtonCallback(
                newValue, "select_query");
          });
        },
        items: querySelectOptions
            .map<DropdownMenuItem>((map) {
          return DropdownMenuItem(
            value: map.name,
            child: Text(map.name),
          );
        }).toList(),
      ), // DropdownButtonFormField
    ), // Container
  ), // Form