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Getting a Promise from Redux Actions

"Great!", you’re thinking...just what the world needs: another blog post about Promises in Redux! Don’t leave yet; this one’s different.

Posted in Coding
March 30, 2018 - 2 min read

Let’s start off with the problem. I manage a few popular form libraries, and I often get the question:

How can I use redux-saga or redux-observable to submit my form via a side-effect?

I have to answer, “Well… the form library is expecting the onSubmit function to return a Promise to know when it is submitting, so...” At least with Redux Form, because all of its state was managed in Redux, including whether or not the form was currently being submitted, it was possible to let users dispatch the START_SUBMIT and STOP_SUBMIT actions themselves, rather than allowing Redux Form to manage that for them via the Promise. But, if you take your form state out of Redux, you’re just sort of screwed…

Crying emoji

Until now.

Sweat-Smile emoji

What if you had a way to create an asynchronous function that dispatched a START action when it was called, and resolved or rejected the returned Promise when either a RESOLVE or REJECT action was dispatched? That would totally solve this problem. Right?

💥 React Redux Promise Listener 💥

The name is not the catchiest on NPM, but... I’ve just released React Redux Promise Listener, a library that solves just this problem. The API looks something like this:

<MakeAsyncFunction
listener={promiseListener}
start="START_ACTION_TYPE" // the type of action to dispatch when this function is called
resolve="RESOLVE_ACTION_TYPE" // the type of action that will resolve the promise
reject="REJECT_ACTION_TYPE" // the type of action that will reject the promise
>
{(asyncFunc) => (
<SomeFormLibrary onSubmit={asyncFunc}>
...
<button type="submit">Submit</button>
</SomeFormLibrary>
)}
</MakeAsyncFunction>

The promiseListener comes from a piece of Redux middleware that must be installed. By default, the values passed around are kept in action.payload, but there are config options that let you read and write those from anywhere in the actions.

Conclusion

It should be a lot easier now to use async side-effect Redux libraries with other async components, like routers, that were built on the assumption of Promises being “how async is done” in Javascript.

❤️ Enjoy! ❤️

© 2021 Erik Rasmussen