Deeds

A tiny library to generate strongly typed action creators from a set of reducers for Redux.

The core of Redux is dispatching actions containing some data and then writing reducers that act on the current state and that data. Keeping the data in the action in sync with that required by the reducer can be tricky. TypeScript helps but only if you strongly type the reducers and strongly type the actions which can be a chore. I found myself writing out a lot of boilerplate to keep things in sync and make TypeScript happy.

This library simplifies a lot of this by automatically generating strongly typed action creators from a set of reducers.

Examples

import { createStore } from "redux";
import { reducer, actionCreators, Deed } from "deeds";

const reducers = {
  add: (state: number, val: number): number => {
    return state + val;
  },
  del: (state: number, val: number): number => {
    return state - val;
  }
}

const store = createStore(reducer(reducers), 1);
const actions = actionCreators<typeof reducers>();

store.dispatch(actions.add(5));
// state is now 6.
store.dispatch(actions.del(3));
// state is now 3.

let action = actions.add(4);
// action is strongly typed at this point but mostly you will not need that and
// can just cast to Deed.
let untyped: Deed = action;
store.dispatch(untyped);

immer

Optionally this supports using immer for an immutable state:

import { createStore } from "redux";
import { Draft } from "immer";
import { reducer, actionCreators, Deed } from "deeds/immer";

interface State {
  value: readonly number;
}

const reducers = {
  add: (state: Draft<State>, val: number): void => {
    state.value += val;
  },
  del: (state: Draft<State>, val: number): void => {
    state.value -= val;
  }
}

const store = createStore(reducer(reducers), { value: 1 });
const actions = actionCreators<typeof reducers>();

store.dispatch(actions.add(5));
// state is now 6.
store.dispatch(actions.del(3));
// state is now 3.

deeds/immer exports functions with the same names as those in deeds. While some of those are just re-exports from deeds right now semantic versioning will increased on the basis that you are only using the exports of one of deeds or deeds/immer for any given store.

Uninitialized stores

The reducer you pass to Redux's createStore must accept an undefined store state and the reducer returned from the reducer call matches that signature, however in order to avoid having to define every reducer as accepting an undefined state it will simply throw an exception if an undefined state is ever passed. This works fine if you always pass an initialized state to createStore but will be a problem if you create an uninitialized store and then use an action to initialize it. In this case you will need to create your own reducer to handle the unitialized case:

import { createStore } from "redux";
import { baseReducer, Deed } from "deeds";

interface InitializeAction {
  type: "INITIALIZE";
  value: number;
}

const reducers = {
  add: (state: number, val: number): number => {
    return state + val;
  },
  del: (state: number, val: number): number => {
    return state - val;
  }
}

// `baseReducer` is identical to `reducer` but only accepts an initialized state.
const reducer = baseReducer(reducers);
const store = createStore((state: number | undefined, action: Deed | InitializeAction) => {
  if (!state) {
    if (action.type == "INITIALIZE") {
      return action.value;
    }

    // Early action?
    state = 0;
  }

  return reducer(state, action);
});
const actions = actionCreators<typeof reducers>();