I have a kotlin object and a java class like:
KotlinObject.kt
object KotlinObject{
....
}
JavaClass.java
class JavaClass {
...
}
and a kotlin function to check:
fun foo(cls: Class<*>): Any {
if (cls is kotlin's object) { //how to do this?
return ? //wanna return object's instance
} else {
return cls.newInstance()
}
}
I can pass kotlin object or java class to this function:
foo(KotlinObject::class.java)
foo(JavaClass::class.java)
so is it possible to tell which one is kotlin's object?
Thanks to @Alexey Romanov for pointing out in the comments that the Kotlin class information is available from Class<*>.
fun foo(cls: Class<*>) {
if (cls.kotlin.objectInstance != null)
println("KotlinObject")
else
println("Other class")
}
My original approach was to mimic Kotlins KClass.objectInstance.
I keep this for reference but please use the solution above.
fun foo(cls: Class<*>) {
val objectInstance = cls.declaredFields.firstOrNull {
it.type == cls && it.name == "INSTANCE"
}
if (objectInstance != null)
println("KotlinObject")
else
println("Other class")
}
Be aware that any Java Singleton using the name 'INSTANCE' for the singleton field will also be reported as Kotlin object in that case.
Got it!
object KotlinObject{}
class JavaClass {}
fun foo(cls: KClass<*>) {
if (cls.objectInstance != null)
println("It's a Kotlin object")
else
println("It's NOT a Kotlin object")
}
fun main(args: Array<String>) {
foo(KotlinObject::class)
foo(JavaClass::class)
}
Output:
It's a Kotlin object
It's NOT a Kotlin object
If, for some reason, you must pass the Java class, then I couldn't figure out any way to do this. I think all the distinction is then gone.
NOTE: This works even if JavaClass is defined in a Java file. Every object in Kotlin is of a KClass type regardless of how and where it was defined. That is, ::class works on any object in Kotlin.