Do you know when to use produceState() in Jetpack Compose?

This is the answer to Adroid Dev Challenge No. 6 that I posted a couple of days ago.

The challenge consisted of showing you two pieces of code that performed identical functionality. You were supposed to guess what Jetpack Compose API we can use instead.

And the answer to that challenge is surprise-suprise 🎉…. produceState!

Many of you have guessed that - great job! ProduceState() is not a complex concept to grasp, but it's an interesting one.

Let's see what it does. 👀

ProduceState is, in fact → LaunchedEffect() + remember {}. If we look inside produceState(), we'll see these two concepts combined:

In our example, we had 2 states:

- Loading state ⏳

- Result ✅ This can be easily achieved with produceState():

Looks neater than our solution with LaunchedEffect and the ViewModel, right? 👍

In the challenge post, many people pointed out that exposing a nullable flow from the ViewModel is bad practice. That's correct, and that's also a reason why produceState is more appropriate here.

In our initial challenge, we achieved the same functionality using:

1️⃣ LaunchedEffect + two remember{} statements

2️⃣ ViewModel + exposing a Flow

So why bother with produceState? 🤔

The reason why produceState() works best for our outcome is because:

1️⃣ It's way less code and is more readable. Having to track only one point of accumulation of values is always easier than having to update them separately. 📉

2️⃣ ProduceState() conflates results. This means we always get the "freshest" value and skip everything in between. Theoretically, we don't need to show the loading animation if our request is rapid. Conflation helps here. Such functionality is advantageous in scenarios where only the latest value is important, such as a taxi application. 🚕💨

3️⃣ Just like LaunchedEffect - produceState() will cancel the underlying coroutine when it leaves the composition, helping with memory leaks. 🧹

ProduceState() is definitely a "niche" API, but it does have its purpose.