How to have less repetition, ideally using `when`,...

# getting-started

[Ray Rahke]

How to have less repetition, ideally using when, for the following

if (Gameengine.input.keysdown(Keys.W) {
  // ..
}
if (Gameengine.input.keysdown(Keys.A) {
  // ..
}
if (Gameengine.input.keysdown(Keys.S) {
  // ..
}
if (Gameengine.input.keysdown(Keys.D) {
  // ..
}

I want something like

when Gameengine.input.keysdown() {
  Keys.W -> {}
  Keys.A -> {}
  Keys.S -> {}
  Keys.D -> {}
}

I know why this is semantically incorrect. but is there an equivalent?

[Joffrey]

How is Gameengine.input.keysdown defined? Can it return the set of keys that are pressed?

If those are directions in the game, you might not want a when because both A and W could be pressed at the same time to go diagonally, right? In this case you might want to run both the branch for the A and the one for the W

[Ray Rahke]

It does not return anything beyond true/false for the given key

[Ray Rahke]

yeah you are right when is not right for player movement since you should be able to trigger both at the same time

[Ray Rahke]

still, is there anything like this?

[Ray Rahke]

maybe a map?

[Ray Rahke]

Map(
Keys.W to {}
Keys.A to {}
)

[Joffrey]

If a when were valid for you (you only want one branch) and you had to use the API of GameEngine exactly as it is designed here, then I'm afraid the only when-based option would be to use a subject-less when like:

when {
    Gameengine.input.keysdown(Keys.W) -> {}
    Gameengine.input.keysdown(Keys.A) -> {}
    Gameengine.input.keysdown(Keys.S) -> {}
    Gameengine.input.keysdown(Keys.D) -> {}
}

But that's not helping much if your problem was the repetition.

[Joffrey]

If Gameengine.input.keysdown() returned a set of pressed keys instead, you could do things like:

val keysDown = GameEngine.input.keysdown() // assuming you could get a set here
when {
  Keys.W in keysDown -> {}
  Keys.A in keysDown -> {}
  Keys.S in keysDown -> {}
  Keys.D in keysDown -> {}
}

[Joffrey]

You could also configure a map with the keyboard keys as the map keys, and some lambdas as values, yes. But then you would still need to access that map to actually run the lambdas:

val keyHandlers = mapOf<Key, () -> Unit>(
  Keys.W to { ... }
  Keys.A to { ... }
  Keys.S to { ... }
  Keys.D to { ... }
)

val keysDown = GameEngine.input.keysdown() // still assuming you could get a set here
keysDown.forEach {
    keyHandlers[it]?.invoke() // or use getValue to make it fail on unknown keys
}

[Ray Rahke]

thanks

[Youssef Shoaib [MOD]]

Here's an idea:

object keysdown {
  operator fun contains(key: Keys) = Gameengine.input.keysdown(key)
}

Then you can do:

when {
  Keys.W in keysdown -> ...
  Keys.A in keysdowm -> ...
}

[Ruckus]

Another idea:

fun Keys.isDown() = Gameengine.input.keysdown(this)

when {
    Keys.W.isDown() -> ...
    Keys.A.isDown() -> ...
}