Mastering Kotlin

Private constructors

It's possible to modify the visibility of a constructor. This is sometimes desirable in order to limit how or what can instantiate a class. A common example of this in Java would be the factory pattern in which the instantiation of a class can only be performed by some factory method.

For example, to make a primary constructor private, we can add the private keyword before the constructor keyword when defining the private constructor:

class School private constructor(val name: String)

In this example, School can longer be instantiated because its only constructor is private. To modify the visibility of a secondary constructor, we once again add the visibility modifier before the constructor keyword:

class School private ...