Getters and Setters in Kotlin

Question

In Java, for example, I can write getters on my own (generated by IDE) or use Annotations like @Getter in lombok - which was pretty simple.

Kotlin however has getters and setters by default. But I can't understand how to use them.

I want to make it, lets say - similar to Java:

private val isEmpty: String
        get() = this.toString() //making this thing public rises an error: Getter visibility must be the same as property visibility.

So how do getters work?

Answer 1

Getters and setters are auto-generated in Kotlin. If you write:

val isEmpty: Boolean

It is equal to the following Java code:

private final Boolean isEmpty;

public Boolean isEmpty() {
    return isEmpty;
}

In your case the private access modifier is redundant - isEmpty is private by default and can be accessed only by a getter. When you try to get your object's isEmpty property you call the get method in real. For more understanding of getters/setters in Kotlin: the two code samples below are equal:

var someProperty: String = "defaultValue"

and

var someProperty: String = "defaultValue"
    get() = field
    set(value) { field = value }

Also I want to point out that this in a getter is not your property - it's the class instance. If you want to get access to the field's value in a getter or setter you can use the reserved word field for it:

val isEmpty: Boolean
  get() = field

If you only want to have a get method in public access - you can write this code:

var isEmpty: Boolean
    private set 

due to the private modifier near the set accessor you can set this value only in methods inside your object.