Ducks++: Redux Reducer Bundles

This is an enhancement to the original Ducks proposal. Basically, the concept is keep redux functionality as modular as possible. The original Ducks standard requires that for each module the associated {actionTypes, actions, reducer} should be kept in one file. The additional rules in Ducks++ is to define a string constant inside the duck to determine where the state is stored in the store; this crucially allows the selectors to also be defined in the same file. Finally the default export should be an object which includes the {actionTypes, actions, reducer, selectors, mountPoint}.

Example

A duck module for handling error state in an app:

// errors.js

import {createSelector} from 'reselect';
import {fromJS, List} from 'immutable';

const STORE_MOUNT_POINT = 'globals/errors';
const ADD_GLOBAL_ERROR = 'UTILS:ADD_GLOBAL_ERROR';
const CLEAR_GLOBAL_ERRORS = 'UTILS:CLEAR_GLOBAL_ERROR';

// Actions
const addGlobalError = error => ({
    type: ADD_GLOBAL_ERROR,
    payload: error
});

const clearGlobalErrors = () => ({
    type: CLEAR_GLOBAL_ERRORS
});

// Selectors
const getGlobalErrors = state => state[STORE_MOUNT_POINT].get('errors');
const selectGlobalErrors = createSelector(
    getGlobalErrors,
    errors => errors.toJS()
);

const initialState = fromJS({
    errors: []
});

//reducer
const reducer = (state = initialState, action = {}) => {
    switch (action.type) {
        case ADD_GLOBAL_ERROR:
            return state.set('errors', state.get('errors').push(action.payload));
        case CLEAR_GLOBAL_ERRORS:
            return state.set('errors', List());
        default:
            return state;
    }
};

// interface
const errors = {
    mountPoint: STORE_MOUNT_POINT,
    actionTypes: {ADD_GLOBAL_ERROR, CLEAR_GLOBAL_ERRORS},
    actionCreators: {addGlobalError, clearGlobalErrors},
    selectors: {selectGlobalErrors},
    reducer
};
export default errors;

Usage

// store.js
import { combineReducers } from 'redux';
import * as ducks from './ducks/index';

function mapDucksToReducers(ducks) {
    const reducers = Object.keys(ducks).map(key => {
        const duck = ducks[key];
        return {
            [duck.mountPoint]: duck.reducer
        };
    });
    return Object.assign({}, ...reducers);
}

const rootReducer = combineReducers(mapDucksToReducers(ducks));
export default rootReducer;

A react error display component:

// Warning.js
import React from 'react';
import {connect} from 'react-redux';
import globalErrors from 'state/errors';

Snackbar.propTypes = {
    label: React.PropTypes.string
};

const Warning = ({dismissAction, errors=''}) => (
    <div>
        {errors}
        <button onClick={dismissAction}>Dismiss</button>
    </div> 
);

Warning.propTypes = {
    dismissAction: React.PropTypes.func.isRequired,
    errors: React.PropTypes.string
};

const mapStateToProps = state => ({
    errors: globalErrors.selectors.selectGlobalErrors(state)
});

const mapDispatchToProps = dispatch => ({
    dismissAction: () => dispatch(globalErrors.actionCreators.clearGlobalErrors())
});

const WarningContainer = connect(
    mapStateToProps, mapDispatchToProps
)(Warning);

export {WarningContainer as default, Warning};

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Photo credit to Airwolfhound.

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