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Encapsulating State Management Library

Tydux is a state management library implemented in TypeScript with a strong focus on encapsulation, type safety and immutability. It can be used standalone or hook into existing Redux-based (or compatible) application.

The key concepts are:

  • You define your state in designated classes or objects.
  • Only commands are allowed to alter the state. Commands are implemented as classes with methods. Every method defines a valid state transition. Hence, only commands are responsible for the state manipulation.
  • Commands are only accessible within a facade. The facade provides the initial state, a read-only access to the state and a stream to subscribe state changes.
  • While commands provide fine-grained methods for state manipulation, the facades provide more coarse-grained methods. For example, a facade could provide a method to load a todo list from the server. To do so, the facade method would 1. use a command method to clear the current state, 2. load the list from the server and 3. use a command method to update the state with the received list.
  • The facade is responsible for handling async operations (e.g. HTTP calls) and uses the commands to change the state accordingly.
  • Consumers of the facade can access a read-only version of the state or subscribe to state changes via an RxJS Observable.
  • You can have as many facades as you like with each of them containing their own commands and state.

If you know Redux:

Tydux shares the concept of state, actions, reducer and selectors but differs in the way they are implemented:

  • Actions and their reducers are implemented together and are called commands. No more action type string identifier!
  • Only facades can access commands
  • A facade provides a read-only stream of state changes

Key benefits:

  • implement "divide and conquer"
  • type safety
  • enforced immutability
  • class-based API
  • ... which works well with Angular's dependency injection

Installation

Install Tydux and all required peer-dependencies:

npm install @w11k/tydux @w11k/rx-ninja rxjs redux redux-devtools-extension.

Quick Overview Demo

Well will need at least a state, the commands and the facade.

Create the state class:

You can implement the state with a class or a plain JavaScript object. Classes are a bit more convenient but remember that you must not use inheritance and that the class only contains fields.

export class TodoState {
  todos: ToDo[] = [
    {isDone: false, name: 'learn TypeScript'},
    {isDone: true, name: 'buy milk'},
    {isDone: true, name: 'clean house'},
  ]
}

Create the commands:

Commands are grouped within a class and can alter the state via this.state. Only the direct field members of the state object can be changed, not the attributes of nested object.

export class TodoCommands extends Commands<TodoState> {

    clear() {
        this.state.todos = [];
    }
    
    setTodoList(todos: ToDo[]) {
        this.state.todos = todos;
    }
    
    toggleTodo(name: string) {
        this.state.todos = this.state.todos.map(
            it => it.name === name ? {...it, isDone: !it.isDone} : it
        )
    }
    
}

Create the facade:

After we created the state and commands, we combine them within a facade.

export class TodoFacade extends Facade<TodoCommands> {

  constructor() {
    super(
        'todos',                // the 'mount point' within the global state 
        new TodoCommands(),     // commands instance defined above
        new TodoState()         // initial state
    );
  }

  /**
   * in our facade we can do synchronous or asynchronous stuff (action or effect)
   */
  async loadTodoListFromServer() {
    this.commands.clear();
    const list = await fetch("/todos");
    this.commands.setTodoList(list);
  }
  
  /**
   * simple delegate to a command method
   */
  toggleDoneStateOf(t: ToDo) {
    this.commands.toggleToDo(t.name);
  }

}

Bootstrap:

After we created the state, commands and facade, we can bootstrap Tydux.

  1. Create a TyduxStore and provide the global initial state (optional, defaults to {}). Every facade's state is part of this global state.
  2. Register the TyduxStore as global store.
  3. Instantiate the facade(s).
// Create and register the tydux store
const tyduxStore = createTyduxStore();      // 1.
setGlobalStore(tyduxStore);                 // 2.

// instantiate every facade once
const todoFacade = new TodoFacade();        // 3.  

Usage:

// get the current state
const todos: ToDo[] = todoFacade.state.todos;

// subscribe to state changes
todoFacade.subscribe(state => {
    const todos: ToDo[] = state.todos;
});

// call facade methods
todoFacade.loadTodoListFromServer();

Documentation

Patron

❤️ W11K - The Web Engineers

❤️ theCodeCampus - Trainings for Angular and TypeScript


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