Reselect Selector That Invokes Another Selector

Reselect is a popular library in the world of React and Redux that enhances the performance of our applications by optimizing the memoization process. In this article, we’ll delve into the concept of invoking one selector from another in ReSelect, a technique that allows us to create more dynamic and reusable selectors for our state management needs.

Here’s a scenario: you have a set of selectors in your React-Redux application, and for some reason, you need to reuse the logic of one selector inside another selector. This is where invoking a selector from another selector comes into play. By doing this, you can prevent code duplication, keep your selectors concise, and improve the maintainability of your codebase.

Let’s walk through an example to better understand how to reselect selector that invokes another selector:

Suppose we have two selectors, `getUsers` and `getActiveUsers`. The `getUsers` selector fetches all users from our Redux state, while `getActiveUsers` filters out only the active users from the list. If we want to display a list of active users in a specific component, we can utilize the logic defined in the `getActiveUsers` selector within the `getUsers` selector by invoking it.

To achieve this, we can modify the `getUsers` selector to call `getActiveUsers` internally and return the filtered list of active users. Here’s how you can implement this:

Javascript

import { createSelector } from 'reselect';

const getUsers = state =&gt; state.users;

const getActiveUsers = createSelector(
  getUsers,
  (users) =&gt; users.filter(user =&gt; user.active)
);

const getActiveUsersCount = createSelector(
  getActiveUsers,
  (activeUsers) =&gt; activeUsers.length
);

const getActiveUsersList = createSelector(
  getActiveUsers,
  (activeUsers) =&gt; activeUsers.map(user =&gt; user.name)
);

export { getActiveUsersCount, getActiveUsersList };

In the example above, `getActiveUsersCount` and `getActiveUsersList` selectors invoke the `getActiveUsers` selector internally to derive additional data based on the active users in our state.

By adopting this approach, we keep our code modular, avoid redundant logic, and make our selectors more composable. This not only improves the readability of our code but also simplifies the process of maintaining and extending our selector functions in the future.

Remember, the key to utilizing selectors effectively in your React-Redux project is to strike a balance between granularity and reusability. By breaking down complex logic into smaller, composable selectors and invoking them within one another when needed, you can create a scalable and efficient state management system.

So, the next time you find yourself needing to reuse the logic of one selector in another, don’t hesitate to reselect and invoke – your future self (and your teammates) will thank you for the clean and organized codebase!

Related posts:

Contact Info