Using React Hooks for global Redux stores

When hooks came out there were various articles suggesting Redux might no longer be needed, and ripostes like these which argue (rightly) that useReducer is not a replacement of Redux as it’s cumbersome for a global store:

Then as a counter-counter argument some suggested using React Context as a solution to share the state and dispatcher throughout the app:

However this method has a significant drawback to performance — as per Caveats in the React docs, whenever a new object reference is passed into <Provider value={..}> , all consumers will be re-rendered. This is different to react-redux’s connect() function which will re-render the component when the parts of the state you’re interested in change.

Today I needed a global store when using Gatsby as it completely unmounts the React tree on navigation changes, thus losing any state created by components. Unfortunately their solution for this, at least by itself, remains awkward for passing state down to deeper components and dispatches back up.

Making a global redux store with hooks

It turns out making a store with hooks is quite simple. It consists of two components:

1. The class which holds store state (redux does this with a function called createStore() but same difference)

2. A hook to receive parts of the store the component is interested in, as well as the dispatch function to make updates

Let’s look at the class first:

Simple right? How we use this will become apparent when we put it into practice. You might notice we even dispatch actions to Redux Devtools :)

Once we’ve created our store we need to be able to access it in any component, that’s where the hook comes in:

The hook:

1. Takes a part of the existing store state and assigns it to state

2. On mount adds a listener for store changes, and on unmount removes it

3. When the state changes it checks if the part that we’re interested in has changed. If it has then we update our state with `setState` which causes the component to re-render.

And finally the app code

Let’s look at a scenario where we want a light and dark theme.

Great we’ve created our store and reducer. Now let’s look at how we can use the hook to access the theme and change it.

And all that running together:

We can tersely access parts of any global store anywhere in the app and our component will only re-render if those parts of the store changed :tada: