Data Classes

Data Classes

We frequently create a class to do nothing but hold data. In such a class some standard functionality is often mechanically derivable from the data. In Kotlin, this is called a data class and is marked as data:

data class User(val name: String, val age: Int)

The compiler automatically derives the following members from all properties declared in the primary constructor:

• equals()/hashCode() pair,
• toString() of the form "User(name=John, age=42)",
• componentN() functions corresponding to the properties in their order of declaration,
• copy() function (see below).

If any of these functions is explicitly defined in the class body or inherited from the base types, it will not be generated.