Create a custom reducer

3 min

This article provides an example custom reducer in FrontEnd\modules\blueprints\example\src\Store\Reducers.ts

Create a custom state for the reducer.

type CounterState = Readonly<{
  total: number;
}>;
const initialCounterState: CounterState = { total: 0 };

Create the reducer. Configured Commerce uses Immer reducers, but traditional reducers are also supported.

import createTypedReducer, { createTypedReducerWithImmer } from "@insite/client-framework/Common/CreateTypedReducer";
import { Draft } from "immer";
const customReducerUsingImmer = createTypedReducerWithImmer(initialCounterState,  
{  
	"Custom/Immer/Add":  
		(draft: Draft<CounterState>, action: { amount: number }) => {  
			draft.total += action.amount;  
	},  
});

const customReducerTraditional = createTypedReducer(initialCounterState, {  
	"Custom/Traditional/Add":  
		(state: CounterState, action: { amount: number }): CounterState => ({  
		// You would normally use `...state` to copy the existing state, but this only has one property.  
		total: state.total + action.amount,  
	}),  
});

Add the reducer to the global list.

import { AnyAction, reducers } from "@insite/client-framework/Store/Reducers";
(reducers as any).customReducerUsingImmer = customReducerUsingImmer;  
(reducers as any).customReducerTraditional = customReducerTraditional;

Create CustomGlobalState from ApplicationState and new states.

export type CustomGlobalState = {
  customReducerUsingImmer: CounterState;
  customReducerTraditional: CounterState;
} & ApplicationState;

Create CustomActions from base AnyActions and new reducer types.

type Reducers = {
  customReducerUsingImmer: typeof customReducerUsingImmer;
  customReducerTraditional: typeof customReducerTraditional;
};
export type CustomActions = Parameters\<Reducers[keyof Reducers]>[1] | AnyAction;

You can find the widget for the custom reducer at FrontEnd\modules\blueprints\example\src\Widgets\ CustomReducerWidget.tsx.