Hi everyone glad to be here I am trying to create an extensi kotlinlang #getting-started

Hi everyone, glad to be here. I am trying to create an extension property, but I want to avoid creating the object that the getter returns every time I am accessing the property. Does anyone have an idea how I can implement that please?

Shawn

12/24/2018, 4:50 AM

you could maybe assign it as a top-level val and then return it as the result of the

get()

private val _foo = Foo()

val OtherType.foo: Foo
  get() = _foo

Smorg

12/24/2018, 4:55 AM

thanks @Shawn; that should work; but the object I am trying to create requires another property from the class (or object) on which I am creating the extension

Shawn

12/24/2018, 4:56 AM

if the property this object depends upon is on the instance of a class, then it doesn’t make sense to have a “static” object that depends upon that property

and you’ll have to instantiate a new one of these objects with each instance of the class you’re extending

serebit

12/24/2018, 4:57 AM

it wouldn’t be idiomatic, but you could keep a private

MutableMap

with the class instance as the key and the property as the value

if the property doesn’t exist for a given instance, create it and store it, otherwise get it from the map

Shawn

12/24/2018, 4:58 AM

maybe I’m misunderstanding the problem, but how would you access the private map from an extension val?

it doesn’t seem like something you’d want to expose with a public getter, even if returned as a

Map

rather than a

MutableMap

but I could be wrong ¯\_(ツ)_/¯

Smorg

12/24/2018, 5:06 AM

Thanks guys @Shawn @serebit. I probably should just move the property to the class instead.

👍 2

serebit

12/24/2018, 6:49 PM

@Shawn

private val map = mutableMapOf<Int>().withDefault { 0 }

val Foo.bar get() = map[this]

Shawn

12/24/2018, 6:52 PM

I don’t think that’ll work since

map

is private within

Foo

oh, I see, as like a separate top-level map

serebit

12/24/2018, 6:53 PM

yeah

3 Views

#getting-started Join Slack