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split your business logic easily / handle your page state / handle animation state within your business logic

build License: MIT

Alfreed # studio flutter management library. This lib is used for our apps and is open for all.

This force split business logic / view for your pages.

This is not a state management lib
You can combine Alfreed with bloc, rxdart or riverpod for reactive update.
See examples for more infos...(bloc, riverpod example coming next)

Install #

Add alfreed in your pubspec and import it.

import 'package:alfreed/alfreed.dart';

Getting Started #

Create a page builder #

class SecondPage extends AlfreedPage<MyPresenter, MyModel, ViewInterface> {
  SecondPage({Object? args}) : super(args: args);

  AlfreedPageBuilder<MyPresenter, MyModel, ViewInterface> build() {
    return AlfreedPageBuilder(
      key: ValueKey("presenter"),
      builder: (ctx, presenter, model) {
        return Scaffold(
          appBar: AppBar(title: Text(model.title ?? "")),
          // ... you page widgets are here
      presenterBuilder: (context) => MyPresenter(),
      interfaceBuilder: (context) => ViewInterface(context),

Every build or defered to let our navigation beeing responsible for building them. (see routing section).

  • builder: build your flutter page content (widgets...)
  • presenterBuilder: build your presenter (business logic class)
  • interfaceBuilder: build your view interface (business logic call this class to interact with our application without knowing flutter). Goal is to hide flutter from our business logic. (Example: showSnackBar(String message) Without any context in parameters)
  • key(optionnal): used to get a reference to the presenter

Note: we extends [AlfreedPage] to handle hot reload. Without hot reload we could remove this layer.

Create a presenter #

Create a presenter extending Presenter class. This is where you write your business logic. There is only and only one presenter instance available in the widget tree.

An instance of this will be available in the builder method seen in previous stage (Create a page builder).

class MyPresenter extends Presenter<MyModel, ViewInterface> {
    // ... write you business logic methods here

Create state class #

Basically this will contain everything you want to show on your page. This model is a simple class where you can wrap models ValueNotifier or Stream.

class ViewInterface extends AlfreedView {
  ViewInterface(BuildContext context) : super(context: context);

  /// ... all your attributes you want to use in your page

  void showMessage(String message) {
    final snackBar = SnackBar(content: Text(message));

Routing #

You can push our page widget in your app router.
Like this:

Route<dynamic> route(RouteSettings settings) {
  switch( {
      case "/":
        return MaterialPageRoute(builder: FirstPage());
        return MaterialPageRoute(builder: SecondPage());

Persist page state after disposed page #

Use case: you want to navigate to a tab and keep your page state across rebuild. You can use this

Use rebuildIfDisposed parameter.


class SecondPage extends AlfreedPage<MyPresenter, MyModel, ViewInterface> {
  AlfreedPageBuilder<MyPresenter, MyModel, ViewInterface> build() {
    return AlfreedPageBuilder(
      key: ValueKey("presenter"),
      builder: (ctx, presenter, model) => Scaffold(appBar: AppBar(title: Text(model.title ?? ""))),
      presenterBuilder: (context) => MyPresenter(),
      interfaceBuilder: (context) => ViewInterface(context),
      rebuildIfDisposed: false, /// this force the builder to not recreate our presenter. Only content will be rebuilt after recreating page. 

Responsive state management #

Our build method contain a special context named AlfredContext. This class contains a Device attribute you can use to make your view for different size of devices.

We used twitter bootstrap sizes ref to create range of devices

Device type can be :

  • phone (0px - 576px])
  • tablet ([576px - 992px])
  • large ([992px - 1200px])
  • xlarge (more than 1920px large)

Example of using:

AlfreedPageBuilder<MyPresenter, MyModel, ViewInterface>(
  key: ValueKey("presenter"),
  builder: (ctx, presenter, model) {
    return Scaffold(
      floatingActionButton: ctx.device < Device.large()
          ? FloatingActionButton(
              backgroundColor: Colors.redAccent,
              onPressed: () =>
                  presenter.addTodoWithRefresh("Button Todo created"),
              child: Icon(Icons.plus_one),
          : null,
  presenterBuilder: (context) => MyPresenter(),
  interfaceBuilder: (context) => ViewInterface(context),

Here our floating button will be available only for devices smaller than large (phone and tablets).

Animations #

To create animations on your page you can use AlfreedPageBuilder factories:

  • AlfreedPageBuilder<MyPresenter, MyModel, ViewInterface>.animated(...) for single animation controller
  • AlfreedPageBuilder<MyPresenter, MyModel, ViewInterface>.animatedMulti(...) or multiple animations controller Then you have access to builder methods for your animations.

Basically animations are accessed through a map where you name them. This can help finding each animations back when you need them.

Animation(s) controller(s) and their animations will be available in your presenter and AlfreedPageBuilder builder methods within context.


 AlfreedPageBuilder<MyPresenter, MyModel, ViewInterface>.animated(
  singleAnimControllerBuilder: (ticker) {
    var controller =
        AnimationController(vsync: ticker, duration: Duration(seconds: 1));
    var animation1 = CurvedAnimation(
        parent: controller, curve: Interval(0, .4, curve: Curves.easeIn));
    var animation2 = CurvedAnimation(
        parent: controller, curve: Interval(0, .6, curve: Curves.easeIn));
    return {
      '': AlfreedAnimation(controller, subAnimations: [animation1, animation2])
  animListener: (context, presenter, model) {
    if (model.animate) {
      context.animations!.values.first.controller.forward(); //SIMPLIFY
  builder: (ctx, presenter, model) => ...,
  presenterBuilder: (context) => MyPresenter(),
  interfaceBuilder: (context) => ViewInterface(context),

Access to animations within presenter and start the first one:


Page arguments #

You can pass arguments from routing directly to your presenter like this

Route<dynamic> route(RouteSettings settings) {
  switch ( {
    case '/second':
      return MaterialPageRoute(builder: SecondPage(args: settings.arguments));
      return MaterialPageRoute(builder:;

now you can access args directly inside your presenter using:


Developper hot reload #

Presenter has a rebuildOnHotReload that will trigger each time user hot reload and call onInit again. By default rebuildOnHotReload is False, so state will be preserved.

Handle behavior on hot reload #

Override onReassemble in your presenter.

Test #

Get presenter ref #

Use AlfreedUtils to get a reference of your presenter instance.

var presenter = AlfreedUtils.getPresenterByKey<MyPresenter, MyModel>(
    tester, ValueKey("presenter"));
  • The Key must be unique and added to the AlfreedPageBuilder seen on step (Create a page builder)
  • The application must be started using a pumpWidget
  • the page is correctly build

Get data from child widget #

You can directly get your viewmodel from an Alfreedpage child like using this :

final myModel = PresenterInherited.dataOf<MyPresenter, MyModel>(context);

Mock presenter #

Prefer using a real presenter but in some case this helps.

Doc incoming

VsCode snippets #

Preferences > User snippets

"Alfreed template": {
		"prefix": "alf",
		"description": "create an Alfreed templated page",
		"body": [
			"import 'package:flutter/material.dart';",
			"import 'package:alfreed/alfreed.dart';",
			"class ${1:name}ViewModel {}",
			"class ${1:name}ViewInterface extends AlfreedView {",
			"  ${1:name}ViewInterface(BuildContext context) : super(context: context);",
			"class ${1:name}Page extends AlfreedPage<${1:name}Presenter, ${1:name}ViewModel, ${1:name}ViewInterface>  {",
			"  ${1:name}Page({Object? args, Key? key}) : super(args: args, key: key);",
			"  @override",
			"  AlfreedPageBuilder<${1:name}Presenter, ${1:name}ViewModel, ${1:name}ViewInterface build() {",
			"    return AlfreedPageBuilder(",
			"      key: ValueKey('presenter'),",
			"      presenterBuilder: (context) => ${1:name}Presenter(),",
			"      interfaceBuilder: (context) => ${1:name}ViewInterface(context),",
			"      builder: (context, presenter, model) => null, //TODO",
			"    );",
			"  }",
			"class ${1:name}Presenter extends Presenter<${1:name}ViewModel, ${1:name}ViewInterface> {",
			"  ${1:name}Presenter() : super(state: ${1:name}ViewModel());",
	} logo

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split your business logic easily / handle your page state / handle animation state within your business logic

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