@reduxjs/toolkit/src/entities/state_selectors.ts

The official, opinionated, batteries-included toolset for efficient Redux development

import { createSelector } from 'reselect'
import { EntityState, EntitySelectors, Dictionary, EntityId } from './models'

export function createSelectorsFactory<T>() {
  function getSelectors(): EntitySelectors<T, EntityState<T>>
  function getSelectors<V>(
    selectState: (state: V) => EntityState<T>
  ): EntitySelectors<T, V>
  function getSelectors(
    selectState?: (state: any) => EntityState<T>
  ): EntitySelectors<T, any> {
    const selectIds = (state: any) => state.ids

    const selectEntities = (state: EntityState<T>) => state.entities

    const selectAll = createSelector(
      selectIds,
      selectEntities,
      (ids: T[], entities: Dictionary<T>): any =>
        ids.map((id: any) => (entities as any)[id])
    )

    const selectId = (_: any, id: EntityId) => id

    const selectById = (entities: Dictionary<T>, id: EntityId) => entities[id]

    const selectTotal = createSelector(selectIds, ids => ids.length)

    if (!selectState) {
      return {
        selectIds,
        selectEntities,
        selectAll,
        selectTotal,
        selectById: createSelector(selectEntities, selectId, selectById)
      }
    }

    const selectGlobalizedEntities = createSelector(selectState, selectEntities)

    return {
      selectIds: createSelector(selectState, selectIds),
      selectEntities: selectGlobalizedEntities,
      selectAll: createSelector(selectState, selectAll),
      selectTotal: createSelector(selectState, selectTotal),
      selectById: createSelector(selectGlobalizedEntities, selectId, selectById)
    }
  }

  return { getSelectors }
}