Inline classes are a powerful feature in Kotlin that allows developers to create lightweight wrappers around values without the runtime overhead of additional objects. They provide type safety and encapsulation while maintaining performance.
Inline classes in Kotlin are a way to create a new type that holds a single value but doesn't introduce the overhead of creating a separate object at runtime. They are particularly useful when you need to wrap primitive types or add semantic meaning to existing types.
To declare an inline class, use the inline keyword before the class keyword. Here's a basic example:
inline class Password(val value: String)In this example, Password is an inline class that wraps a String. At runtime, instances of Password will be represented as String values.
Let's look at a more comprehensive example to demonstrate the use of inline classes:
inline class Meters(val value: Double) {
fun toKilometers(): Double = value / 1000
operator fun plus(other: Meters): Meters {
return Meters(value + other.value)
}
}
fun calculateDistance(start: Meters, end: Meters): Meters {
return end + start
}
fun main() {
val distance1 = Meters(5000.0)
val distance2 = Meters(2500.0)
val totalDistance = calculateDistance(distance1, distance2)
println("Total distance: ${totalDistance.value} meters")
println("Total distance in km: ${totalDistance.toKilometers()} km")
}In this example, we define an inline class Meters that wraps a Double value. We add a method to convert to kilometers and overload the plus operator. This allows us to perform calculations with Meters objects while maintaining type safety and readability.
To further enhance your understanding of Kotlin's type system and performance optimizations, consider exploring these related topics:
Inline classes are a powerful tool in Kotlin for creating efficient, type-safe wrappers around values. By understanding and utilizing this feature, you can write more expressive and performant code in your Kotlin projects.