The main purpose of data class is hold data , in koltin compiler automatically creates following
- getters and setters for the constructor parameters -
- hashCode()
- equals()
- toString()
- copy()
- componentN() function
following condition should be fullfilled to create a data class
- primary constructor needs to have at least one parameter.
- All primary constructor parameters need to be marked as val or var.
- Data classes cannot be abstract, open, sealed or inner.
to exclude a property for generated implementation declare it inside data class
data class Person(val name:String?=null, val age:Int? = null ){ var excludeProp:Int = 34 fun personDetails():String?{ return "name=$name Age=$age" } } fun main(args: Array<String>) { // val p1 = Person () var p1 = Person ("Justin", 27) val p2 = Person ("Justin", 27) val p3 = Person ("Justin", 26) println(p1) // println(p1 == p2) // true println(p1 == p3) // false p1.excludeProp = 90 println(p1.excludeProp) // 90 println(p2.excludeProp) // 34 // use copy() when want to change some of properties of object , rest properties are unchanged val newPerson = Person("Karl Bruce", 18) val oldPerson = newPerson.copy(age = 90) println(oldPerson) // Person(name=Karl Bruce, age=90) //Data classes and destructuring declarations val p5 = Person("Chris", 45) val (name , age ) = p5 print("name = $name age =$age") //name = Chris age =45 //call function print( p5.personDetails() ) // name=Chris Age=45 } 
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