An interesting trick some may not know about using `MutableState`. When using state as a delegate yo...

# compose

[Alexander Maryanovsky]

An interesting trick some may not know about using MutableState. When using state as a delegate you often have the compiler refuse to do smart casts (e.g. if (x != null) { x.function() } doesn’t compile). The alternative is to just assign the state value to the variable (i.e. var xState by remember { mutableStateOf(…) } and then val x = xState.value). A better alternative is to use destructuring on the state - it turns out MutableState.component2 returns a setter of the value. So you can do:

val (x, setX) = remember { mutableStateOf(...) }

and then you have the value in x (which smart casts will work on), and a setter in setX. This is particularly convenient with composables like TextField.

[Albert Chang]

A caveat is that without a recomposition x won’t be updated even after you call the setter with a new value, which isn’t the case if you use var x by remember { mutableStateOf(…) }.

[Alexander Maryanovsky]

Indeed.

You could define

operator fun <T> MutableState<T>.component3() = this

and use

val (x, setX, xState) = remember { mutableStateOf(...) }

😉

[Kachinga Mulenga]

How do i get to the level where all this makes sense 🙂 ?

I'm currently at the level where i just know how to write var x by remember { mutableStateOf(…) }.

[Zach Klippenstein (he/him) [MOD]]

i wish Kotlin had something like swift’s if let x = xState