Building React with Redux and Redux-Saga in a Monorepo

A monorepo setup can streamline development when building a large-scale React application with Redux and Redux-Saga. This article takes a high-level look at how to structure Redux and Redux-Saga in a monorepo, focusing on API handling and service integration.

1. Why Use a Monorepo?

In a monorepo, you manage multiple packages or services within a single repository. This setup offers the following advantages:

• Code sharing: Shared logic, utility functions, and constants can live in a single place.

• Single source of truth: You avoid version mismatches across services, which ensures consistency.

• Easy dependency management: Updating dependencies across the project becomes easier with tools like Yarn Workspaces or Lerna.

2. Architecture Overview

In this setup, the monorepo contains:

• React frontend: The UI, responsible for user interactions and dispatching Redux actions.

• Shared libraries: Utility functions, constants, and TypeScript interfaces/models shared across services.

• API services: Backend microservices or API endpoints that the frontend interacts with.

Here's a high-level architecture of this system:

3. API Flow in Redux with Redux-Saga

In this ecosystem, Redux handles the application state, while Redux-Saga manages side effects, such as asynchronous API calls.

Step-by-step flow:

1. Action Dispatch: A user triggers an action in the UI (e.g., a form submission).

2. Redux-Saga Middleware: Redux-Saga listens for specific actions (e.g., FETCH_DATA_REQUEST) and captures these to handle side effects.

3. API Request: The saga makes an API request using an asynchronous call like call(apiService.fetchData, payload).

4. Response Handling: The saga handles the API response. On success, it dispatches a FETCH_DATA_SUCCESS action, which updates the Redux store with the API data. On failure, it dispatches a FETCH_DATA_FAILURE action for error handling.

5. Store Update: The Redux store updates its state, which causes the React UI to re-render based on the new state.

// Example Saga
import { call, put, takeEvery } from 'redux-saga/effects';
import apiService from '@shared/apiService'; // Shared API service

function* fetchData(action) {
  try {
    const response = yield call(apiService.fetchData, action.payload);
    yield put({ type: 'FETCH_DATA_SUCCESS', data: response.data });
  } catch (error) {
    yield put({ type: 'FETCH_DATA_FAILURE', error });
  }
}

function* watchFetchData() {
  yield takeEvery('FETCH_DATA_REQUEST', fetchData);
}

export default watchFetchData;

4. Monorepo Structure

A typical monorepo structure for this project would look like this:

/monorepo
  /packages
    /frontend
      /src
        /components
        /redux
          /sagas
          /actions
          /reducers
    /shared
      /src
        /apiService.js
        /constants.js
    /backend
      /api
        /src
          /routes
          /controllers

• Frontend: Contains the React app with Redux actions, reducers, and sagas.

• Shared: A shared package that includes reusable utilities, API service functions, and constants used across frontend and backend.

• Backend: A backend package responsible for handling API routes and logic.

5. Benefits of Redux-Saga in a Monorepo

• Side Effect Management: Redux-Saga enables complex side-effect management, like retrying failed API requests or debouncing API calls to prevent flooding.

• Separation of Concerns: Redux handles state management, while Redux-Saga isolates asynchronous logic, ensuring clean and maintainable code.

• Reusability: API services and logic can be shared between different packages in the monorepo, ensuring DRY principles across frontend and backend services.

6. API Services in the Monorepo

In this architecture, the API services could be defined in the shared package, ensuring that both the frontend and backend can use them. This ensures that API service logic and data transformations are consistent across different parts of the application.

Here’s a shared API service example:

// apiService.js
import axios from 'axios';

const apiService = {
  fetchData: async (payload) => {
    const response = await axios.get(`/api/data/${payload.id}`);
    return response;
  },
};

export default apiService;

7. Conclusion

A monorepo setup with React, Redux, and Redux-Saga can offer a scalable, maintainable structure for handling large applications with shared logic and consistent API integration. By centralizing API service logic, side effects management, and state handling, the system ensures clean code practices and streamlined collaboration across teams.