```fun Message diffUtilEquals o Any Boolean if o is Message kotlinlang #announcements

fun Message.diffUtilEquals(o: Any): Boolean {
    if (o !is Message) return false
    if (id != o.id) return false
    return true
}

fun TextMessage.diffUtilEquals(o: Any): Boolean {
    if (!super.diffUtilEquals(o)) return false
    if (o !is TextMessage) return false
    if (text != o.text) return false
    return true
}

nwh

11/30/2019, 7:52 PM

Is there a reason you're using extension functions instead of normal inheritance? If you own both the

Message

and

TextMessage

classes then why not use a good old fashioned

open fun

and override it

👍🏻 1

molikuner

11/30/2019, 8:03 PM

There is no way of overwriting an extension function, as they are statically resolved.

open class A
class B : A()

fun A.x() = println("A")
fun B.x() = println("B")

val a: A = B()
a.x()

This prints

instead of

ursus

11/30/2019, 8:22 PM

@nwh because its domain layer model and diffutil is ui layer, so I didnt want dirty it (nor create ui layer model)

molikuner

11/30/2019, 8:31 PM

https://pl.kotl.in/amql0ZACw May be the only option, if you really need it, but I would prefer writing an extra ui layer model instead of this!

ursus

11/30/2019, 9:05 PM

@molikuner yea I had something like that in mind, however the overriding was supposed to share code from Message, as my Message has id, and some other fields. Yes I can workaround it via baseDiffEquals and call it manually, but then if I were to have some more inheritance, Id need to spell out all the super classes

bummer

matter of fact I do, since example of hierachy is TextMessage : ContentMessage : Message. so I need to

fun TextMessage.diffEquals {
   messageDiffEquals
   contentMessageDiffEquals
   my fields ..
}

right?

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