KClass
- Kotlin course
- Advanced
- Lesson 61/83
- 5 min
Learn class info with ::class and KClass.
Class info with KClass
KClass holds the runtime info of a class. The ::class syntax gives you a KClass reference. It provides info about members, constructors and supertypes.
Example: val kc = String::class; println(kc.simpleName). This prints String. Use kc.isData to check if it is a data class and kc.members to list members. Reflection inspects types at runtime.
simpleName and isData
The simpleName property of KClass gives the short name of the class. Flags like isData, isAbstract and isSealed describe the class nature.
Example: data class User(val name: String). User::class.isData returns true. User::class.simpleName gives "User". These flags let you branch on the type structure at runtime.
Practice Print the Person class name
Define class Person(val name: String). In main print the result of Person::class.simpleName with println.
Starter code
// Person class: name property
// in main print the class name via reflectionSample solution
class Person(val name: String)
fun main() {
println(Person::class.simpleName)
}Expected output
Person
Questions and answers
Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.
1 Which syntax gets a KClass reference of a class?
- getClass()
- .class
- classOf<>()
- ::class Correct answer
Explanation: In Kotlin ::class gives a KClass reference.
2 Complete the KClass reference
val kc = String____val kc = String::classExplanation: ::class gives a KClass reference.
3 Match the KClass parts
| Term | Meaning |
|---|---|
String::class |
KClass reference |
simpleName |
Type name |
isData |
Data class flag |
members |
Members |