I try to observe any significant difference betwee...

# compose

[marcinmoskala]

I try to observe any significant difference between using stable and unstable types with Strong skipping mode enabled, and I have trouble finding any substantial example. The key difference is that unstable types are compared with ===, and stable first with ===, and if it returns true by ==. To observe the difference, I would need to literally provide a new object that is equal to the previous one. I cannot imagine any reasonable code that would do that. Do you have any examples/experiences in this?

[Stylianos Gakis]

Creating a new list each time, which is == but not === is one of the very common ways where this happens

[marcinmoskala]

Can you show me an example?

[marcinmoskala]

Why creating a new list if it has the same elements?

[marcinmoskala]

Ok, I guess if this list is a part of an object that is fetched from some API 🤔

[Stylianos Gakis]

If it's created in composition but not inside a remember would be a good example I think

[marcinmoskala]

Ok, I can see it

[marcinmoskala]

Do you have any example why can't an unstable object be compared by == as well?

[Stylianos Gakis]

Yeah, in case a class has implemented the equals function incorrectly.
Or if it has mutable state internally which is not backed by mutable state. Although I suppose even === in that case might be giving the wrong results

[marcinmoskala]

Yes, compose is not dealing with mutable objects well as they cannot be observed.

[marcinmoskala]

I try to understand the class of objects that:
1. Are safe to be used in compose
2. Are not immutable

[marcinmoskala]

I guess it is about things like view models 🤔

[Albert Chang]

This is very common. Consider this example.

@Composable
fun Screen(
    text: String,
    list: List<String>,
) {
    Column {
        Text(text)
        List(list)
    }
}

@Composable
fun List(
    list: List<String>,
) {
    LazyColumn(list)
}

When text changes, the whole Screen, including List, will be recomposed, and List can only be skipped if strong skipping mode is enabled.

[Albert Chang]

Or maybe I misunderstood your question.

[marcinmoskala]

In this question I assumed strong skipping mode is enabled, so there List is not recomposed.

[gmz]

and stable first with ===, and if it returns true by ==

if === returns true, then there is no point in doing also ==, given that === is stronger than ==. Usually the instance equality check is the first line of a proper equals() implementation (and probably the runtime never checks stable types with ===, but only ==)