Is there any mechanism to access a component of pa...

# korge

[jeff]

Is there any mechanism to access a component of particular type (e.g. MyCustomComponent : Component) that is attached to a view IFF it is already attached (i.e. don't create one if it doesn't exist)?

[jeff]

I tried this code which works great in JVM but throws a ClassCastException in Kotlin/JS

inline fun <reified T : Component> BaseView.getComponentOrNull(): T? {
    return getOrCreateComponentOther<T> {
        return null
    }
}

[Deactivated User]

Do you mean, any type? You can use getOrCreateComponentUpdate , getOrCreateComponentMouse ... Initially it was just getOrCreateComponent but was converted into that to improve performance in K/N. What's your use case / why do you need the method you want to write?

[jeff]

Yeah, any type. I have a custom component that handles some logic & animation. I'd like to be able to "clear" it (i.e. find & detach any component of that type from a given view) without having to maintain a reference to each one.

[jeff]

Technically I could do that with getOrCreateComponent but in the case where none previously existed I'd end up constructing one only to immediately throw it away

[jeff]

Open to suggestions, including better ways to structure a game if this seems to you like a weird thing for someone to want to do 🙂

[Deactivated User]

So the component is not an standard component, right? It is something you use internally?

[jeff]

correct, just extends Component (not, say, UpdateComponent)

[Deactivated User]

We should definitely rework the component part to have only one method. The current API is weird, but was designed to avoid a performance hit on Kotlin/Native, so as long as they improve it, we will be able to simplify it again. There is a getOrCreateComponentOther
We can just add variants like getComponentOrNull you can even make a PR to add them:
https://github.com/korlibs/korge-next/blob/721d78c9ae1c7ce5c3a5b999a30eaeca46c93a8[…]rge/src/commonMain/kotlin/com/soywiz/korge/baseview/BaseView.kt

Can you make a PR adding those getComponent*OrNull methods?

Alternatively, View implements the Extra interface, that support adding extrinsic properties without weak maps, so you can attach stuff there yourself and externally define your own code for a custom component system.

But well, as said, PRs are welcome 🙂

[jeff]

More than happy to add a PR. The version I have seems to run afoul of Kotlin/JS's runtime type checking, since it throws a CCE there (but not on JVM). If I can figure out why and fix it, I'll submit it.

[jeff]

I'll also look into Extra, that seems promising

[jeff]

thanks!