updux/docs/recipes.md

Recipes

Mapping a mutation to all values of a state

Say you have a todos state that is an array of todo sub-states. It's easy enough to have the main reducer map away all items to the sub-reducer:

const todo = new Updux({
    actions: {
        review: action('REVIEW'),
        done: action('DONE',payload<int>()),
    },
    mutations: {
        review: () => u({reviewed: true}),
        done: () => u({done: true}),
    },
});

const todos = new Updux({ initial: [] });

todos.addMutation( 
    todo.actions.review, 
    (_,action) => state => state.map( todo.upreducer(action) )  
);
todos.addMutation(
    todo.actions.done, 
    (id,action) => u.map(u.if(u.is('id',id), todo.upreducer(action))),
);

But updeep can iterate through all the items of an array (or the values of an object) via the special key *. So the todos updux above can be rewritten as:

const todos = new Updux({
    subduxes: { '*': todo },
});

todos.addMutation(
    todo.actions.done, 
    (id,action) => u.map(u.if(u.is('id',id), todo.upreducer(action))), 
    true
);

The advantages being that the actions/mutations/effects of the subdux will be imported by the root updux as usual, and all actions not overridden by a sink mutation will trickle down automatically.

Usage with Immer

While Updux was created with Updeep in mind, it also plays very well with Immer.

For example, taking this basic updux:

import Updux from 'updux';

const updux = new Updux({
    initial: { counter: 0 },
    mutations: {
        add: (inc=1) => state => ({ counter: state.counter + inc })
    }
});
    

Converting it to Immer would look like:

import Updux from 'updux';
import { produce } from 'immer';

const updux = new Updux({
    initial: { counter: 0 },
    mutations: {
        add: (inc=1) => produce( draft => draft.counter += inc ) } 
    }
});
    

But since typing produce over and over is no fun, groomMutations can be used to wrap all mutations with it:

import Updux from 'updux';
import { produce } from 'immer';

const updux = new Updux({
    initial: { counter: 0 },
    groomMutations: mutation => (...args) => produce( mutation(...args) ),
    mutations: {
        add: (inc=1) => draft => draft.counter += inc 
    }
});