[Kotlin] implicit getterr && setter (field keyword)

// Shorter version
class AnotherAlternativeCustomer (val name: String,var age: Int, val address: String = "") {
    var approvered: Boolean = false
    set(value) {
        if (age>21)
            field = value
        else
            println("You cannot approve a customer under 21 years old.")
    }
}

c.age = 19
c.approvered = true // will print message

getter:

// Shorter version
class AnotherAlternativeCustomer (val name: String,var age: Int, val address: String = "") {
    val nextAge
    get() = age + 1
}