Understand Fields and Properties in Kotlin

How Kotlin implicitly implements field, getter and setter function for you when you declare a property?

Properties and fields terminologies in Kotlin sometimes is a bit confusing because technically, Kotlin doesn’t have Fields. You can’t declare a field. Everything is Properties!

However, to avoid confusion, I prefer to define Fields and Properties separately based on the following:

• Fields are private member variables of a class. Memory is allocated.
• Properties are public or protected getter or setter functions which allow you to access to the private fields.

I like to define like this because it helps my understanding and it also makes things a lot easier to explain.

Implicit Field, Implicit Getter/Setter

Let’s look at this example. name is a property.

class Person {
    var name = "Vincent"
}

When you declare a property like this, Kotlin implicitly creates field, getter and setter functions for you.

In Java decompiled code, it looks like this:

public final class Person {
   @NotNull
   private String name = "Vincent"…