scottt2/design-patterns-in-dart

Gang of Four (GOF) design patterns implemented in Dart. Contributions welcome!

Design Patterns in Dart

Welcome! The intent of this repo is to provide

1. Examples for each of the 23 Gang of Four design patterns
2. An introduction to the Dart programming language

Please see Getting Started for more information on how to run the examples.

Table of Contents

Behavioral Patterns

• Chain of Responsibility
• Command
• Interpreter
• Iterator
• Mediator
• Memento
• Observer
• State
• Strategy
• Template Method
• Visitor

Creational

• Abstract Factory
• Builder
• Factory Method
• Prototype
• Singleton

Structural Patterns

• Adapter
• Bridge
• Composite
• Decorator
• Facade
• Flyweight
• Proxy

Getting Started

Each example has its own directory, inside which is a short readme and a sole Dart file. To run the example, make sure you have Dart installed and then just do

dart <example directory>/<example name>.dart

Take State, for example:

> dart state/state.dart

The light switch is off.
Toggling the light switch...
  Touching the Stateful...
  Handler of StatusOff is being called!
The light switch is on.

If you have any questions or see any issues, please feel free to file an issue.

Enjoy!

-Tyler

design-patterns-in-dart's Issues

late is not correct for _next in chain_of_responsibility

when you define _next late, for last Logger we get error (or any logger that we dont need _next ) because this variable is not initilized.
we must change it to Nullable inctance instead, like below:
Logger? _next;

Dart patterns

Improve decorator pattern example

In the decorator pattern example, the two classes are different. The StarbucksDecorator is not decorating an existing coffee object but creating a new coffee object every time. This class should take a coffee object in its constructor and work on it.
Let me know what you think about it. I'd love to contribute to this.

Add UML Diagrams

I think especially for programmers who don't know exactly how each pattern works, it would be nice to have some UML Diagrams to make the concept more clear

What does ._internal() mean in Singleton Pattern?

Hello, please, explain, what does ._internal() mean in Singleton Pattern?

class Me {
  static final Me _singleton = new Me._internal();
  static final String _name = "Tyler";

  factory Me() {
    return _singleton;
  }

  static String get name => _name;
 
  @override
  String toString() => "Hello, my name is $name.";

  Me._internal();
}

Me._internal()