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Reducer ​

Overview ​

Reducers define how the store's state changes in response to actions. They handle incoming actions and update the state accordingly. This ensures that the application's state remains predictable and immutable.

Defining a Reducer ​

Reducers in this library are based on @ngrx/store and leverage reducerBase from @k5cjs/store to simplify state management.

Example Reducer Definition ​

typescript
import { reducerBase, stateBase } from '@k5cjs/store';
import { EntityAdapter, createEntityAdapter } from '@ngrx/entity';
import { createReducer, Action } from '@ngrx/store';

import { actions } from './users.actions';
import { State, User } from './users.type';

export const adapter: EntityAdapter<User> = createEntityAdapter<User>();

const initialState: State = adapter.getInitialState({
  ...stateBase(),
});

export function reducer(state: State | undefined, action: Action): State {
  return createReducer(
    initialState,

    ...reducerBase(adapter, actions),
  )(state, action);
}
import { reducerBase, stateBase } from '@k5cjs/store';
import { EntityAdapter, createEntityAdapter } from '@ngrx/entity';
import { createReducer, Action } from '@ngrx/store';

import { actions } from './users.actions';
import { State, User } from './users.type';

export const adapter: EntityAdapter<User> = createEntityAdapter<User>();

const initialState: State = adapter.getInitialState({
  ...stateBase(),
});

export function reducer(state: State | undefined, action: Action): State {
  return createReducer(
    initialState,

    ...reducerBase(adapter, actions),
  )(state, action);
}

See Also:

Explanation ​

  • The adapter manages entity operations such as adding, updating, and removing users.
  • The initialState sets up the default state using adapter.getInitialState().
  • The reducerBase(adapter, actions) automatically generates handlers for standard CRUD actions.

Conclusion ​

Reducers are responsible for defining how state changes based on actions. With reducerBase, @ngrx/entity, and structured action handling, managing state remains efficient and scalable.