How do I initialize a final field in Kotlin?

Question

Let's say I declared a final field with private final String s (Java) or val s (Kotlin). During initialization I want to initialize the field with the result of a call to a remote service. In Java I would be able to initialize it in the constructor (e.g. s = RemoteService.result()), but in Kotlin I can't figure out how to do that because as far as I can tell the field has to be initialized in the same line it's declared. What's the solution here?

Solution 1

You can set val value in init block:

class MyClass {

    val s: String

    init {
        s = "value"
    }

}

Solution 2

You can also initialize the value with by lazy the value will be initialized the first time it is referred. An example

val s by lazy { RemoteService.result() }

kotlin will guess the type of s from the return type of the expression.