Create a Feature Store

There are 2 Options to create a new Feature Store.

Option 1: Extend FeatureStore

todo-feature-store.ts

import { FeatureStore } from 'mini-rx-store';
import { Todo } from './todo';

export interface TodoState {
  todos: Todo[];
  selectedTodoId: number
}

export const initialState: TodoState = {
  todos: [],
  selectedTodoId: undefined
};

export class TodoFeatureStore extends FeatureStore<TodoState> {
  constructor() {
    super('todo', initialState)
  }
}

Extending the FeatureStore requires to pass the feature key (e.g. 'todo') and the initial state. We have to provide a TypeScript interface to FeatureStore to get type safety: FeatureStore<TodoState>.

Option 2: Functional creation method

We can create a Feature Store with createFeatureStore.

const todoFs: FeatureStore<TodoState> = createFeatureStore<TodoState>('todo', initialState);

The following examples will be based on Option 1 (Extend).

Lazy state initialization with setInitialState

In some situations, you do not know yet the initialState when creating a Feature Store. For that reason you can initialize the state later with setInitialState.

Example:

export class TodoFeatureStore extends FeatureStore<TodoState> {
  constructor() {
    super('todo', undefined); // Initial state is undefined! 
  }
  
  // Called later
  init(initialState: TodoState) {
    this.setInitialState(initialState);
  }
}

danger

An error will be thrown, if you call setState before an initial state was set (via the constructor or setInitialState).