Playing with Reflection API and property reference...

# getting-started

[Zinedine Bedrani]

Playing with Reflection API and property reference I tried something like this :

data class Point(val x:Int, val y:Int)

 val p = Point(5,13)

   val getter1 = Point::x
   val getter2: (Point) -> Int  = Point::x
 
    println(getter1(p)) // 5
    println(getter2(p)) // 5

What I don’t understand is why with getter1 I was able to get reflection information about x for example I could do something like :

println(getter1.visibility) // PUBLIC
   println(getter1.returnType) // <http://kotlin.Int|kotlin.Int>

while with getter2 I can’t, even if I use the @OptIn(ExperimentalReflectionOnLambdas::class)
with println(getter2.reflect()?.returnType) the result is null.

[Joffrey]

The types of getter1 and getter2 are not the same. By specifying a wider type on getter2, you're losing the specificities of the more precise type of Point::x (KProperty1<Point, Int>). Using the actual KProperty type comes with extra information.

A simple analogy would be val getter3: Any = Point::x - do you expect to be able to access visibility and returnType here?

[Joffrey]

Using .reflect() on the getter2 function will just give you a KFunction, not really information about the actual property x

[Zinedine Bedrani]

No I don’t Expect that but (Point) -> Int is a function type, so r`eflect()` should return KFunction, isn’t it ? so I don’t understand why reflect() doesn’t return KProperty.Getter in this case, or Am I wrong ?

[Zinedine Bedrani]

Ah OK I see