astx-redux-util

The astx-redux-util library promotes several redux reducer composition utilities, which blend multiple reducers together forming a richer abstraction through functional decomposition (i.e. higher-order functions).

Reducer composition is not new. Redux itself provides the innovative combineReducers utility which allows you to fuse individual reducers together to build up the overall shape of your application state.

The most prevalent astx-redux-util utility is reducerHash(), which lets you combine sub-reducers in such a way as to eliminate the switch statement commonly used to delineate action type.

Additionally, astx-redux-util promotes other reducer compositions that can be used in conjunction with one another.

Comprehensive Documentation

Complete documentation can be found at https://astx-redux-util.js.org/, which includes both API details, and a Dev Guide with full and thorough examples!

Install

npm install --save astx-redux-util

Examples

Basics

The following example uses reducerHash() to combine a set of sub-reducer functions (indexed by the standard action.type), eliminating the switch statement commonly used to delineate action type.

Don't miss the astx-redux-util documentation, which fully explores this example, and details the API.

import { reducerHash } from 'astx-redux-util';
 
export default reducerHash({
  "widget.edit":       (widget, action) => action.widget,
  "widget.edit.close": (widget, action) => null,
}, null);

Joining Reducers

Building on the previous example, our widget now takes on more detail:

• we manage x/y properties (through the standard combineReducers)
• the widget itself can take on a null value (an indication it is NOT being edited)

We manage these new requirements by combining multiple reducers through a functional decomposition (as opposed to procedural code). To accomplish this, we add to our repertoire by introducing joinReducers() and conditionalReducer().

Did I mention that the astx-redux-util documentation, fully explores this example, and details the API?

import * as Redux         from 'redux';
import * as AstxReduxUtil from 'astx-redux-util';
import x                  from '../appReducer/x';
import y                  from '../appReducer/y';
 
export default AstxReduxUtil.joinReducers(
  // FIRST: determine content shape (i.e. {} or null)
  AstxReduxUtil.reducerHash({
    "widget.edit":       (widget, action) => action.widget,
    "widget.edit.close": (widget, action) => null
  }),
 
  AstxReduxUtil.conditionalReducer(
    // SECOND: maintain individual x/y fields
    //         ONLY when widget has content (i.e. is being edited)
    (widget, action, originalReducerState) => widget !== null,
    Redux.combineReducers({
      x,
      y
    })),
 
  null); // initialState

Full Example

Building even more on the prior examples:

• our widget adds a curHash property (which is a determinate of whether application content has changed)

We manage this new property in the parent widget reducer, because it has a unique vantage point of knowing when the widget has changed (under any circumstance, regardless of how many properties are involved).

We accomplish this by simply combining yet another reducer (using a functional approach). This also demonstrates how composition can be nested!

Read all about it! The astx-redux-util documentation fully explores this example, and details the API.

import * as Redux         from 'redux';
import * as AstxReduxUtil from 'astx-redux-util';
import x                  from '../appReducer/x';
import y                  from '../appReducer/y';
import Widget             from '../appReducer/Widget';
 
export default AstxReduxUtil.joinReducers(
  // FIRST: determine content shape (i.e. {} or null)
  AstxReduxUtil.reducerHash({
    "widget.edit":       (widget, action) => action.widget,
    "widget.edit.close": (widget, action) => null
  }),
 
  AstxReduxUtil.conditionalReducer(
    // NEXT: maintain individual x/y fields
    //       ONLY when widget has content (i.e. is being edited)
    (widget, action, originalReducerState) => widget !== null,
    AstxReduxUtil.joinReducers(
      Redux.combineReducers({
        x,
        y,
        curHash: (s=null)=>s // defaulted state placebo reducer (needed by combineReducers())
      }),
      AstxReduxUtil.conditionalReducer(
        // LAST: maintain curHash
        //       ONLY when widget has content (see condition above) -AND- has changed
        (widget, action, originalReducerState) => originalReducerState !== widget,
        (widget, action) => {
          widget.curHash = Widget.hash(widget); // OK to mutate (because of changed instance)
          return widget;
        })
    )
  ), null); // initialState

This represents a very comprehensive example of how Reducer Composition can simplify your life! We have combined multiple reducers into one, applying conditional logic as needed through functional decomposition!