A simple example of using the spread (`...`) operator within a list of widgets conditionally.

widgets_and_conditional_spread_operators.dart

import 'package:flutter/material.dart';

void main() => runApp(MyApp());

class MyApp extends StatelessWidget {
  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: HomePage(shouldBuildList: false),
    );
  }
}

class HomePage extends StatelessWidget {
  final bool shouldBuildList;

  const HomePage({Key key, @required this.shouldBuildList})
      : assert(shouldBuildList != null),
        super(key: key);

  @override
  Widget build(BuildContext context) {
    return SafeArea(
      child: Scaffold(
        body: Column(children: [
          
          // This is where the list is conditionally injected.
          if (shouldBuildList) ...[
            MyCustomCard(data: 'This'),
            MyCustomCard(data: 'is'),
          ],
          
          MyCustomCard(data: 'my'),
          MyCustomCard(data: 'list.'),
        ]),
      ),
    );
  }
}

class MyCustomCard extends StatelessWidget {
  final String data;
  const MyCustomCard({@required this.data}) : assert(data != null);

  @override
  Widget build(BuildContext context) {
    return Card(child: Text(data));
  }
}