Is there a simple way to create a generic type-safe builder that can be used with a lambda? like `fu...

# getting-started

[Joshy Josh]

Is there a simple way to create a generic type-safe builder that can be used with a lambda? like functionName<ClassName> { …className functions}? I know it can be done specifically, but I was wondering if there was a way to create a generic approach. in Kotlin.

[Joshy Josh]

More specifically, where ClassName could be any class passed in the the type.

[Joshy Josh]

I started with this:

interface BaseRobot {
    fun <T> screen(init: T.() -> Unit): T = init as T
}

[Joshy Josh]

It allows to call, but then when using it will perform a cast error or do nothing with no error.

[Shawn]

what exactly are you trying to accomplish with this?

[Joshy Josh]

Basically have a generic way to call object members using a lambda notation, screen<class> { function() }

[Joshy Josh]

Typically, when I create object for this I have to specify the class in the function using a function outside of the class utilizing the type safe builder approach.

[Shawn]

I mean, if you have an instance of the object in question, you could use run, with, or apply

[Joshy Josh]

I did try, but got a casting error.

[Shawn]

care to be be more specific about the error?

[Shawn]

with the limited context of “having a generic way to call object members with a lambda” T.() -> R is the correct approach, but casting the lambda to T will never work (at least the way you’ve written it in your example)

[Joshy Josh]

I stepped away, so I don't have the exact error log, but it was saying I cannot cast type T to Unit. Basically, I was trying to make this function generic...

[Joshy Josh]

fun screen(bot: Bot.()-> Unit): Bot = Bot().apply(bot())

[Joshy Josh]

I was so close. Ended up using this:

[Joshy Josh]

Inline fun <reified T: Any> screen(bot: T.() -> Unit): T? = T::class.java.newInstance().apply { bot() }

[Joshy Josh]

Then I can use it like screen<ScreenObject> { functionsFromScreenObjectClass }