If you implement a Java interface that defines a g...

# getting-started

[Rob Elliot]

If you implement a Java interface that defines a getter:

interface Something {
  String getAConstant();
}

and you want the value of getAConstant to be a constant, is there a less verbose way than this?

class ConcreteSomething : Something {
  private val _constant = "constant value"
  override fun getAConstant(): String = _constant
}

(It's not actually a String, it's calculated by calling other methods on a supertype using a constructor value, just simplifying things.)

[Klitos Kyriacou]

override fun getAConstant() = "constant_value"

(It can thereafter be used as though it were a val, ConcreteSomething().aConstant , but it has to be defined as a function because it's a Java interface.)

[Joffrey]

@Klitos Kyriacou The initializer in the example is a constant string but it's mentioned that in real life the expression is more complex. I think what Rob meant is that the value shouldn't be recomputed every time.

If you define the function this way, the body will be re-evaluated every time, which I think is not what Rob wants.

[Sam]

Related: https://youtrack.jetbrains.com/issue/KT-6653

[Joffrey]

Ah thanks, I was looking for that link!

[Rob Elliot]

Thanks, yes that was what I was getting at, good to know I haven't missed some better way.

[Joffrey]

So yeah I think your best option right now is what you already did: define a private property with initializer, and then just read that property in the explicitly overridden getter function.