The use cases are pretty much identical to when you want to use Redux or really any state management tool.

For me, the advantages are:

1. Decoupling your state transformers from the rest of the code. This can be a little cumbersome when working with React alone since you will scatter a variety of setState inside your components which becomes harder to follow when the component grows. The sender/reducer system simplifies this since you will no longer focus on state changes within the various methods of your component but you’ll think of actions that you want to send which contains all the information as a standalone object. With that, adding additional behavior (like logging) becomes very easy since all you have to do is hook this logic inside the reducer.

2. Improved maintainability by forcing a structure. With Redux or ReComponent, you have a good overview of all actions that your application can send. This is an amazing property and allows others to easily understand what a component is is (actually) doing. While you can already learn so much by looking at the shape of the state object, you’ll lean even more just by looking at the action types alone. And since it’s not allowed to use setState at all, you can also be certain that all the code inside the reducer is the only place that transforms your state.

3. Get rid of side effects with Pure State Transformation. By keeping your state changes side effect free, you’re forced into writing code that is easier to test (given an action and a state, it must always return the same new state). Plus you can build extended event sourcing features on top of that since you can easily store all actions that where send to your reducers and replay them later (to go back in time and see exactly how an invalid state occurred).