Class Reference in Kotlin

Introduction

Class Reference is a fundamental concept every Kotlin developer should understand. Reflection inspects types, properties, and functions at runtime — useful for serialization libraries, DI frameworks, and testing utilities.

Class reference uses ::class syntax. In this tutorial you will learn the syntax, walk through a complete example program, study the sample output, and review best practices so you can apply the concept confidently in your own projects.

Definition

• Class reference uses ::class syntax.
• Returns KClass object with metadata about class.
• Useful for reflection and framework integration.

Syntax

val clazz = MyClass::class

Class Reference in Kotlin Example Program in Kotlin

class Sample

fun main(args: Array<String>) {
    val clazz = Sample::class
    println("Class name: ${clazz.simpleName}")
}

Sample Output

Class name: Sample

When to use

Use reflection sparingly for frameworks and generic utilities; prefer compile-time type safety when possible.

How it works

1. The program starts with a main function — the entry point that runs when you execute the file.

2. val clazz = Sample::class assigns or updates a value used later in the program.

3. The println("Class name: ${clazz.simpleName}") statement writes a line to the console — this produces part of the sample output below.

4. Class reference uses ::class syntax.

5. Run the program in IntelliJ IDEA, Android Studio, or with the Kotlin command-line compiler (kotlinc / kotlin). Compare your console output with the sample output shown below.

Best Practices

• Understand the core idea: class reference uses ::class syntax.
• Prefer readable names and small functions so examples map directly to real projects.
• Run and modify the example — change values and observe how the output changes.

Common Mistakes

• Skipping the example and only reading the definition — hands-on practice cements the concept.
• Copying syntax without understanding nullable vs non-nullable types or scope rules.
• Ignoring compiler warnings that often point to safer alternatives.

Key Points

• Class reference uses ::class syntax.
• Returns KClass object with metadata about class.
• Useful for reflection and framework integration.
• Test the example locally and verify the output matches the sample.
• Experiment by changing input values to see how behaviour changes.

Notes

• Semicolons at the end of statements are optional in Kotlin.