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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