A simple library for applying the Humble Object Pattern in order to create clean, testable widgets.

Features

This package might be helpful to you if:

• a high level of test coverage is required
• you apply test driven development to app development
• you find it difficult to separate UI logic from appearance
• the widgets you create depend on too many details

Usage

Using the library will feel very familiar. Let’s start by creating a simple button as a HumbleStatelessWidget.

1. Write a test! (skip ahead if you still haven’t been converted to TDD ). Be sure to include tests for all logic that is important to you. This may include strings, colors, padding — anything that is necessary to make the widget “right”.

bool testSimpleButtonLogic(){
	bool tapped = false;
	final logic = SimpleButtonLogic(text: 'test', onTap: () {
		tapped = true;
	});
	if (logic.text != 'test') return false;
	logic.onTap();
	if (tapped == false) return false;
	return true;
}

2. Create a plain old Dart object to represent the UI element’s logic.

class SimpleButtonLogic {
	SimpleButtonLogic({required this.text, required this.onTap});

	final String text;
	final Function() onTap;
}

3. Once your class passes it’s tests, you will use it to create your widget. Use the logic getter to access your widget’s logic.

class SimpleButton extends HumbleStatelessWidget<SimpleButtonLogic> {
	SimpleButton(SimpleButtonLogic logic) : super(logic, key: Key('SimpleButton'));

	@override
	Widget build(BuildContext context) {
		return ElevatedButton(
			child: Text(logic.text),
			onPressed: () => logic.onTap(),
		);
	}
}

That’s it! You now have a testable (albeit simple) widget! Take a look at the example folder for creating a HumbleStatefulWidget.

Additional information

The amount of source code in the library is minuscule, and it doesn’t constitute anything new or bleeding-edge. However, use of this library will help the average developer apply high level and highly-esteemed software engineering principles to their code.

Learn more about the Humble Object Pattern here: https://martinfowler.com/bliki/HumbleObject.html.

Contribute at https://github.com/brettlaws/flutter_hop.

Download source code on GitHub

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