Reducer Migration

Reducer Migration Overview

Reducer Migration is something you will reach for often in Redux. It keeps your workflow predictable and makes your intent obvious to reviewers and teammates.

When you learn reducer migration properly, you avoid the guesswork that leads to mistakes and rework. The example below shows the shape you will use in most real Redux projects.

import { createSlice } from '@reduxjs/toolkit';

const counterSlice = createSlice({
  name: 'counter',
  initialState: { value: 0 },
  reducers: {
    increment: (state) => { state.value += 1; },
    addBy: (state, action) => { state.value += action.payload; },
  },
});

export const { increment, addBy } = counterSlice.actions;
export default counterSlice.reducer;

createSlice generates actions and a reducer together; Immer lets you write safe 'mutating' updates.

Reducer Migration Example

const slice = createSlice({ name, initialState, reducers });
const store = configureStore({ reducer: { key: slice.reducer } });
// dispatch(slice.actions.something())

• Start from a minimal Reducer Migration example and grow it only as needed.
• Keep things explicit so Reducer Migration behaves the same for everyone on the team.
• Name things clearly so teammates understand your Reducer Migration at a glance.
• Verify Reducer Migration works as expected before relying on it in important work.

Redux Cheatsheet

Quick Redux Toolkit reference related to reducer migration.

How Reducer Migration Works in Redux

Reducer Migration follows Redux's predictable data flow: components dispatch actions, reducers compute the next state from the previous state and the action, and subscribed components re-render.

createSlice generates actions and a reducer together; Immer lets you write safe 'mutating' updates.

• State lives in a single, read-only store.
• Actions are the only way to describe a change.
• Reducers are pure functions that return the next state.
• Redux Toolkit removes most boilerplate with slices and thunks.

Practical Guidance for Reducer Migration

In modern apps, reducer migration should use Redux Toolkit rather than hand-written Redux. Keep state minimal, colocate logic in slices, and use RTK Query for server data.

Common Mistakes

• Skipping edge cases and error handling when using reducer migration.
• Not verifying the result of reducer migration before moving on.
• Over-complicating reducer migration before you actually need the extra flexibility.
• Ignoring documentation, which makes reducer migration hard for the next person to follow.

Key Takeaways

• Reducer Migration is a core part of working effectively with Redux.
• Start small and keep reducer migration focused on a single goal.
• Apply consistent patterns so reducer migration scales across your project.
• Practise and document reducer migration to keep your workflow maintainable.