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, with some
actions that should percolate to all todos, and some that should only
percolate to one. One way to model this is via updux's splat subduxes
(backed by `updeep`'s own '*'-key behavior).

```
const done = () => (state) => ({...state, done: true});

const todo = new Updux({
    initial: { id: 0, done: false },
    actions: {
        done: null,
        doneAll: null,
    },
    mutations: {
        done,
        doneAll: done,
    },
});

const todos = new Updux({
    initial: [],
    subduxes: { '*': todo },
    actions: { addTodo: null },
    mutations: {
        addTodo: text => state => [ ...state, { text } ]
    }
});

todos.setMutation(
    todo.actions.done,
    (text,action) => u.map(u.if(u.is('text',text), todo.upreducer(action))),
    true // prevents the subduxes mutations to run automatically
);

```

## Usage with Immer

While Updux was created with Updeep in mind, it also plays very
well with [Immer](https://immerjs.github.io/immer/docs/introduction).

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
    }
});

```