Data classes

Creating classes whose primary purpose is to hold data is a common pattern in Kotlin (is a common pattern in other languages too, think of JSON or Protobuff).

Kotlin has a particular kind of class for this purpose:

data class Item(val product: BakeryGood,
  val unitPrice: Double,
  val quantity: Int)

To declare data class, there are some restrictions:

• The primary constructor should have at least one parameter
• The primary constructor's parameters must be val or var
• Data classes can't be abstract, open, sealed, or inner

With these restrictions, data classes give a lot of benefits.