What is the right way of using “greater than”, “less than” comparison on nullable integers in Kotlin?

Question

var _age: Int? = 0

public var isAdult: Boolean? = false
   get() = _age?.compareTo(18) >= 0 

This still gives me a null-safety, compile error,

Answer 1

I used the null coalescing operator to convert from nullable Int? to non-nullable Int:

var age: Int? = 0

public var isAdult: Boolean? = null
   get() = if(age == null) null else (age ?: 0 >= 18)