typesafe-redux

Utilities & helpers for increased type safety in a React + Redux application

Example App

A basic example application (todo list) is provided at examples/todos/ which showcases usage of this library to provide type safety in a React + Redux application.

Creating Actions

This library offers a few different ways of creating actions or action creators, which are outlined below. All methods flow through the actionCreator function.

Flux Standard Actions

The actionCreator method can be used to create flux standard action (FSA) factories, using the structure const creator = customActionCreator(type)<PayloadType>(); to define the action type constant and shape of the payload:

import { actionCreator } from 'typesafe-redux';

// with an object payload:
export const addTodo = actionCreator('ADD_TODO')<{
  id: string;
  text: string;
  completed?: boolean;
}>();
dispatch(addTodo({
  id: 'todo-123',
  text: 'hello world'
}));

// with a simple string payload:
export const deleteTodo = actionCreator('DELETE_TODO')<string>();
dispatch(deleteTodo('todo-123'));
export const completeTodo = actionCreator('COMPLETE_TODO')<string>();
dispatch(completeTodo('todo-123'));

// or with no payload at all:
export const completeAll = actionCreator('COMPLETE_ALL')();
dispatch(completeAll());

Once the action type and payload shape have been defined using actionCreator those values will have types automatically applied when they're used in reducers, so you only have to type them once!

Custom/Complex Actions

The actionCreator method also accepts a callback argument for anytime it's necessary for an action creator to take arguments that differ from the payload shape (e.g. because of autogenerated timestamps or other computed values):

import { actionCreator } from 'typesafe-redux';
export const addTodo = actionCreator('ADD_TODO', (type) => {
  return (text: string, completed: boolean = false) => ({
    type,
    payload: {
      // generate ID in the action creator so it doesn't need to be passed in:
      id: generateId(),
      text,
      completed
    }
  });
});

Identifying Actions in Reducers

Action identification is typically done through a string comparison using action.type, but with typesafe-redux the action creator is capable of determining if it produced a given action via the match method injected into the prototype of action creators made using this library. You can either use this method directly or use the provided isActionFrom helper:

import { isActionFrom } from 'typesafe-redux';
function todos(state: IAppState['todos'] = [], action: Action) {
  if (isActionFrom(action, actions.addTodo)) {
    // The `isActionFrom` type guard strongly types `action.payload` within
    // this block as the payload type defined by the action creator
    return [ ...state, action.payload ];
  }
  // ...
}