Some of you can help me with this little problem? I'm very new to Kotlin and Android development! I don't understand why this snippet of code returns me the following error:
class Catalog { var musicList: List<Music> = ArrayList() } class Music{ var id: String = "" } fun main(args: Array<String>) { var test: Catalog test.musicList[0] = "1" } ERROR:
Variable 'test' must be initialized What is wrong? Thank you all!
You need to instantiate it before invoking the getter of musicList:
fun main(args: Array<String>) { var test = Catalog() test.musicList[0] = "1" } Furthermore, if you are not re-assigning the value of test you can declare it as val:
fun main(args: Array<String>) { val test = Catalog() test.musicList[0] = "1" } You will have other 2 errors after that:
List is immutable so you can't use the operator [] to assign a valueTo solve it, you can use MutableList instead of List.
class Catalog { val musicList = mutableListOf<Music>() } fun main(args: Array<String>) { var test = Catalog() test.musicList += Music("1") } 
in Kotlin you can init variable in two ways.
in your case you don't user lateinit So, you need to init your variable with a default value
var test = Catalog() or if you want to init as null
var test:Catalog? = null 
test