Change a value in mutable list in Kotlin

If you expect few items (maybe 1 or 2?) to be affected,
you can filter the list and then change iLike of the filtered items:

vids!!.filter { it.id == 2 }.forEach { it.iLike = true }

Try this, I'm assuming your Videos structure is a data class defined somewhat like so. data class Videos(val id: Int, val yt_id: String, val title: String, val likes: Int, val kat: String, val ilike: Boolean)

list.forEachIndexed { index, video ->
    video.takeIf { it.id == 2}?.let {
        list[index] = it.copy(ilike = true)
    }
}

You can use find function to find the element with id = 2 and change its property:

vids?.find { it.id == 2 }?.iLike = true

Note: it is a good practice to use question mark if the property is nullable and you unsure whether it is null or not.

I had to change several properties and I had a need to hold the changed object. Therefore following approach worked better for me:

//First, find the position of the video in the list
val videoPosition= list.indexOfFirst {
   it.id == 2
}

//Now get your video by position and make changes
val updatedVideo = list[videoPosition].apply {
   //Make all changes you need here
   ilike = true

   //...
}

//Finally, replace updated video into your list. 
list[videoPosition] = updatedVideo