In code like the below, Kotlin complains that the ...

# getting-started

[Jonathan Lennox]

In code like the below, Kotlin complains that the fields aren't initialized, even though if I copy the code from updateFields into the second constructor it does. Is there a way I can get Kotlin to know the fields are always initialized, without duplicating the code between updateFields and the constructor?

class DemoClass
{
    var field1: Int
        private set
    var field2: Int
        private set

    constructor(f1: Int, f2: Int) {
        field1 = f1
        field2 = f2
    }

    constructor(basef: Int) {
        updateFields(basef)
    }

    fun updateFields(basef: Int) {
        field1 = basef * 2
        field2 = basef + 2
    }
}

[Landry Norris]

You can declare a variable as 'lateinit var' to promise the compiler you will initialize it.

[Haram Kwon]

the easiest way to solve this problem is to initialized the number

class DemoClass
{
    var field1: Int = 0
        private set
    var field2: Int = 0
        private set

    constructor(f1: Int, f2: Int) {
        field1 = f1
        field2 = f2
    }

    constructor(basef: Int) {
        updateFields(basef)
    }

    fun updateFields(basef: Int) {
        field1 = basef * 2
        field2 = basef + 2
    }
}

[Haram Kwon]

@Landry Norris lateinit may not work for primitive types 😞

[Jonathan Lennox]

So initialize it for primitive or nullable, lateinit for non-nullable objects?

[Landry Norris]

Doesn't it force the primitive to be boxed? Slight performance hit, but should work. Guess it doesn't do this.

[Jonathan Lennox]

It still seems like the compiler should be able to figure that out, though.

[Jonathan Lennox]

As long as the method called isn't open.

[Haram Kwon]

Let me know if you find a better way 🙂

[ephemient]

class DemoClass(field1: Int, field2: Int) {
    var field1 = field1
        private set
    var field2 = field2
        private set

    constructor(basef: Int) : this(
        field1 = basef * 2,
        field2 = basef + 2,
    )
}

[Jonathan Lennox]

@ephemient: This doesn't solve the problem of duplicating the code between the constructor and the update method (the idea is that class also allows the updateFields method to be called later to change the values).

[ephemient]

then

class DemoClass(field1: Int, field2: Int) {
    var field1 = field1
        private set
    var field2 = field2
        private set

    constructor(basef: Int) : this(0, 0) {
        updateFields(basef)
    }
}