Proposal to add something like reacts 'useEffect

I thought about adding something like Reacts useEffect to simplify interop with some existing Avalonia Controls (CefGlue for Example)

Browser.create [
    Browser.startUrl "duckduckgo.com"
    // not sure how to trigger
    Browser.useEffect (fun browser -> browser.GoBack())
]

Implementing this feature is not complicated, maybe adding more ‘hook’ for attach und detach could also be helpful for controls that need to be specifically initialised.

Maybe effects should also be located in a new namespace like Avalonia.FuncUI.DSL.Effects, because they introduce side effects to an otherwise pure DSL.

@uxsoft @AngelMunoz @AngelMunoz opinions ?

[JaggerJo]

@Swoorup useEffect allows you to do something with the actual instance of the control. I think it should be executed every time (at least by default).

[AngelMunoz]

Not exactly sure why useEffect is required to access the document in JavaScript at all.

It’s just showcasing that you can do a mutation (hence the useEffect name) on an external element/control of the component it could have been a console.log too, it just shows that technically your component can be written in a pure functional way but allowing it to do side effects

This would translate to this in FuncUI, accessing some global state is easy.

I thought global on a more “global” scale like if you could access things that are at namespace level “like” window it would mean it would have been defined earlier in the module. perhaps I’m just not looking it on the right direction

MediaPlayer.create [
    MediaPlayer.filePath "song.mp3"

    // so something impure with the control
    MediaPlayer.useEffect (fun (player: MediaPlayer) -> 
        if player.state != state.playstate then
            match state.playstate with
            | Play -> player.Play()
            | Pause -> player.Pause()
    )
]

Yeah I think this gives me a better insight on how could they be used, you still need to use your current state to allow it to do what you need.

That could address stateful components coming from other C# libraries indeed. Are there any concerns about F# authored controls? I guess in the end even if you choose F# you still need to to the usual UserControl inheritance and property declaration thing.