Callables

We refer to functions and properties as callables. When appropriately annotated, callables can be invoked from either side of the JNI interface (frontend or backend), execute your code on the other side and return some value.

Functions

For a function to be available on the JVM side, it must be annotated with the @Knee annotation. We support top-level functions and functions nested in @KneeClass declarations, as you can learn in classes. Upward functions (called from K/N, implemented on the JVM) are also available through interfaces.

kotlin
Copy
// Kotlin/Native
@Knee fun topLevelFunction(): Int {
    return 42
}

// Kotlin/JVM
check(topLevelFunction() == 42)

Properties

For a property to be available on the JVM side, it must be annotated with the @Knee annotation. We support top-level properties and properties nested in @KneeClass declarations, as you can learn in classes. Upward properties (called from K/N, implemented on the JVM) are also available through interfaces.

Both var and val properties are supported.

kotlin
Copy
// Kotlin/Native
@Knee val immutableProp: Int = 42
@Knee var mutableProp: Int = 0

// Kotlin/JVM
mutableProp = immutableProp
check(mutableProp == immutableProp)