Function Mocking Demo

main.dart

import 'package:flutter/material.dart';
import 'package:ioc_container/ioc_container.dart';
import 'package:url_launcher/url_launcher.dart';

final flutterDevUri = Uri.parse('https://www.flutter.dev');

///A type alias for the launchUrl's function signature
typedef LaunchUrl = Future<bool> Function(
  Uri url, {
  //We accept nulls here because we cannot use default
  //values in type aliases
  LaunchMode? mode,
  WebViewConfiguration? webViewConfiguration,
  String? webOnlyWindowName,
});

///Composition root. This is where we wire up dependencies
IocContainerBuilder compose() => IocContainerBuilder(
      allowOverrides: true,
    )
      ..addSingletonService<LaunchUrl>(
        //This is how we map the LaunchUrl type on to the actual function
        //Yes, this is a bit clunky, but using it in the app is very simple
        (url, {mode, webOnlyWindowName, webViewConfiguration}) async =>
            launchUrl(
          url,
          mode: mode ?? LaunchMode.platformDefault,
          webViewConfiguration:
              webViewConfiguration ?? const WebViewConfiguration(),
          webOnlyWindowName: webOnlyWindowName,
        ),
      )
      ..add((container) => MyApp(launchUrl: container<LaunchUrl>()));

void main() => runApp(compose().toContainer()<MyApp>());

class MyApp extends StatelessWidget {
  const MyApp({
    required this.launchUrl,
    super.key,
  });

  final LaunchUrl launchUrl;

  @override
  Widget build(BuildContext context) => MaterialApp(
        debugShowCheckedModeBanner: false,
        title: 'Function Mocking Demo',
        theme: ThemeData(
          primarySwatch: Colors.blue,
        ),
        home: Scaffold(
          body: Align(
            child: MaterialButton(
              onPressed: () async {
                await launchUrl(flutterDevUri);
              },
              color: Colors.blue,
              textColor: Colors.white,
              padding: const EdgeInsets.all(40),
              shape: const CircleBorder(),
              child: const Icon(
                Icons.favorite,
                size: 50,
              ),
            ),
          ),
        ),
      );
}