repatch
v1.3.12
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Dispatch reducers
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Dispatch reducers
Repatch is just a simplified Redux, that let you create actions more briefly by dispatching reducers directly.
store.dispatch(state => ({ ...state, counter: state.counter + 1 }));
In this terminology, an action is a function that returns a reducer:
const increment = amount => state => ({
...state,
counter: state.counter + amount
});
store.dispatch(increment(42));
Motivation
Redux has verbose action management. The most of redux projects do not need sctrict action administration. Action types, action creators and the reducer's action handlers are mutually assigned to each other. Repatch's purpose is creating actions briefly.
The simplest way to keep the immutable action controlled dataflow and define actions briefly is dispatching pure functions (as reducers) to the store.
Comparison with Redux
Repatch is
- less verbose
- smaller (the minified version is less than 1 KB)
- faster
than Redux.
Working with Redux
If you have to keep the official Redux in your project, then you can use the redux-repatch or redux-repatch-creator enhancers.
API Reference
Examples
Articles
Repatch - the simplified Redux
Installation
npm install --save repatch
How to use
ES6
import Store from 'repatch';
const store = new Store(initialState);
CommonJS
const Store = require('repatch').Store;
UMD
<script src="https://unpkg.com/repatch/dist/repatch.js"></script>
or the minified bundle:
<script src="https://unpkg.com/repatch/dist/repatch.min.js"></script>
and
const Store = Repatch.Store;
const thunk = Repatch.thunk;
Compatibility with react-redux
Repatch's interface is very similar to Redux, therefore you can use with react-redux.
const unsubscribe = store.subscribe(() => console.log(store.getState()));
store.dispatch(resolveFetchingUsers(users));
unsubscribe();
TODO app in brief
const store = new Store([]);
const addTodo = text => todos => [...todos, { text, checked: false }];
const checkTodo = index => todos => todos.map(
(todo, i) => (i === index ? { ...todo, checked: !todo.checked } : todo)
);
const editTodo = (index, text) => todos => todos.map(
(todo, i) => (i === index ? { ...todo, text } : todo)
);
const removeTodo = index => todos => todos.filter((_, i) => i !== index);
Sub-reducers
We do not need to reduce always the whole state of the store. Repatch also offers a way to combine sub-reducers, those describe a deeply nested property in the state. We just define a helper function that takes a nested reducer as argument, and returns a reducer that reduces the whole state:
const reduceFoo = fooReducer => state => ({
...state,
bar: {
...state.bar,
foo: fooReducer(state.bar.foo)
}
});
Using that we can define easily an action, that sets an x
property in the foo
object:
const setX = x => reduceFoo(state => ({ ...state, x }));
Middlewares
A repatch middleware takes the store
instance, a next
function and the previous reducer
. The middleware can provide a new reducer via the next
function.
Middleware: Store -> Next -> Reducer -> any
Use the addMiddleware
method to chaining middlewares:
const store = new Store(initialState)
.addMiddleware(mw1)
.addMiddleware(mw2, mw3);
Middleware example
This simple logger middleware logs the current- and the next state:
const logger = store => next => reducer => {
const state = store.getState()
const nextState = reducer(state)
console.log(state, nextState)
return next(_ => nextState)
}
const store = new Store(initialState).addMiddleware(logger)
Async actions
The thunk
middleware is useful for handling async actions similar to redux-thunk.
import Store, { thunk } from 'repatch';
const store = new Store(initialState).addMiddleware(thunk);
In thunk async actions reducer returns a function (delegate):
const updateUser = delta => state => async (dispatch, getState) => {
try {
const editedUserId = getState().editedUser;
dispatch(toggleSpinner(true));
await api.updateUser(editedUserId, delta);
await dispatch(fetchUsers());
} catch (error) {
dispatch(state => ({ ...state, error: error.message }))
} finally {
dispatch(toggleSpinner(false));
}
};
It is possible to embed async actions within each other too and awaiting their resolving:
await dispatch(fetchUsers());
Injecting extra argument
It is possible to inject extra arguments into async actions:
import Store, { thunk } from 'repatch';
import api from './api';
import { hashHistory } from 'react-router';
const store = new Store(initialState)
.addMiddleware(thunk.withExtraArgument({ api, hashHistory }));
Then you can access these arguments in your delegates:
const updateUser = delta => state =>
async (dispatch, getState, { api, hashHistory }) => {
// ...
}
This way you can keep your async actions independently from outer instances or side-effects. This practice is useful for testing.
Testing
Sync actions
Testing a reducer is easy:
import * as assert from 'assert';
import { changeName } from './actions';
// ...
it('changeName', () => {
const state = { name: 'john' };
const nextState = changeName('jack')(state);
assert.strictEqual(nextState.name, 'jack');
});
Async actions
For async action tests you need to instantiate the Store
and provide mocked extra arguments.
import Store, { thunk } from 'repatch';
import * as assert from 'assert';
import { fetchUsers } from './actions';
const mockUsers = [{ username: 'john' }];
const mockApi = {
getUsers: () => Promise.resolve(mockUsers)
}
// ...
it('fetchUsers', async () => {
const state = { users: [] };
const store = new Store(state)
.addMiddleware(thunk.withExtraArgument({ api: mockApi }));
await store.dispatch(fetchUsers());
const nextState = store.getState();
assert.deepEqual(nextState.users, mockUsers);
});