If you use a ReadWriteProperty with the by operator is there

Question

If you use a ReadWriteProperty with the by operator is there any possibility to access the underlying delegate Ideally I want to override the toString method but keep using idiomatic code

hfhbd · Answer

```fun main var s String by Print $this$this s = foo println s class Print lt T Any gt private val format T gt String ReadWriteProperty lt Nothing T gt constructor initial T formatter T gt String this formatter value = initial private lateinit var value T override fun getValue thisRef Nothing property KProperty lt gt T = value override fun setValue thisRef Nothing property KProperty lt gt value T this value = value override fun toString String = value format ```

Joffrey · Answer

The door for a more idiomatic solution will be open by the explicit backing fields feature the prototype is already out In the meantime you can declare the delegate in a separate variable and use that variable in the `by` clause

Joffrey · Answer

But I m not sure I understand your goal here Do you want the `toString` of the property `s` to be overridden by that of the delegate

hfhbd · Answer

Yeah I am aware of using another delegate variable ```val sPrint = Print lt String gt $this$this var s String by sPrint s = foo println sPrint println s oops``` But you could print the wrong variable

hfhbd · Answer

The explicit backing field alternative should interesting I will take a look

Joffrey · Answer

I mean the backing field feature will not help with your goal here then One use case is to help access the property delegate but it won t change the fact that the value itself has a different `toString` from the delegate

Joffrey · Answer

The delegate is technically just a way to provide the value After that the value is like any other value What you could do is make the delegate return a wrapper of your value with a different `toString ` but that is not possible for every type because you would need to return a custom subtype of the property type

hfhbd · Answer

Yeah I noticed it too smile It is not possible because type of the variable would be `Print lt String gt ` ideally I want to have `String` I think I will use the first approach Use a separate delegate variable and a custom detekt rule to prevent printing the primitive variable without the formatter

Joffrey · Answer

It doesn t look like delegation is useful here to be frank because nothing happens to `s` You re just creating something on the side so it should look like this something on the side For instance something as simple as ```var s String = foo val formattedS String get = $s$s ```

hfhbd · Answer

In this simple example it is true But the delegate should do more than only formatting slightly smiling face

hfhbd · Answer

okay with this keep it should be possible smile <https github com gradle KEEP blob assign operator proposals assign operator overload md>