Kotlin : How to insert a value of a variable in a name of another variable

Question

Sadly, I failed to find any answer to this question on SO or elsewhere.

I am studying Kotlin and Android development and I wonder how I can insert a value of a variable in a name of another variable. Or if there is another, better solution to this problem I have.

Suppose, my code looks like this:

...
 private fun rollDice() {
    // Create new Dice object with 6 sides and roll the dice
    val dice = Dice(6)
    val diceRoll = dice.roll()

    // Find the ImageView in the layout
    val diceImage: ImageView = findViewById(R.id.imageView)

    // Determine which drawable resource ID to use based on the dice roll
    val drawableResource = when (diceRoll) {
        1 -> R.drawable.dice_1
        2 -> R.drawable.dice_2
        3 -> R.drawable.dice_3
        4 -> R.drawable.dice_4
        5 -> R.drawable.dice_5
        else -> R.drawable.dice_6
    }

    // Update the ImageView with the correct drawable resource ID
    diceImage.setImageResource(drawableResource)

    // Update the content description
    diceImage.contentDescription = diceRoll.toString()
}
...

I wonder if in the "Determine which drawable resource ID to use based on the dice roll" block I could actually use something like this (also, sorry, I don't know the correct syntax yet):

val drawableResource = R.drawable.{"dice_"+ diceRoll.toString()}

This way I could have saved much space and make the code easily extensible, if, for example, I had a 20-sided dice, I still would have needed this single line of code.

Or else I would have needed to add

when(diceRoll){ 
...
20 lines of code here
...
}

How can I solve this problem? Thank you.

Enjoy :) https://stackoverflow.com/a/3476470/11958566 (let me know if it works) — Shlomi Katriel, Aug 14 '22 at 17:02
Yes, I have managed to get it to work, thank you! I am only getting familiar with SO rules, should I update the original post with my solution code for this exact case, or post an answer to my question myself, or something else? I have read somewhere that if a post gets deleted, I lose reputation, and I surely don't want that. What is the correct way? — Tim Kochetkov, Aug 14 '22 at 17:19
I posted an answer below. Will be able to accept it only in 2 days, it seems. — Tim Kochetkov, Aug 14 '22 at 17:36
@ShlomiKatriel Also, I have a question on this for a general case. Could you help, please? Suppose I have to reference something that is not in RESOURCES (just a generic variable somewhere), how do I do that? Is there an existing question on SO already? — Tim Kochetkov, Aug 14 '22 at 17:38
Changing variables by their names is only possible with reflection. check out the following: https://stackoverflow.com/a/58361516/11958566 — Shlomi Katriel, Aug 14 '22 at 19:39
@ShlomiKatriel yes! When I was searching an answer to this original post, I stumbled upon reflection a couple of times, and as I understood, it actually was related. Thank you! — Tim Kochetkov, Aug 14 '22 at 19:54

score 4 · Accepted Answer · answered Aug 14 '22 at 17:34

Thanks to Shlomi Katriel for linking the correct solution to this in comment on the original post.

A way to formulate my question in this context would be exactly as in linked post — "How to get a resource id with a known resource name?"

My solution code for this exact case (changed 2 blocks):

// Determine which drawable resource ID to use based on the dice roll
val drawableResourceId : Int = this.resources.getIdentifier("dice_$diceRoll", "drawable",this.packageName)

// Update the ImageView with the correct drawable resource ID
diceImage.setImageResource(drawableResourceId)

Kotlin : How to insert a value of a variable in a name of another variable

1 Answers1