Prompt Title: Delegation

Yes, in the provided code:

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useCase(private val helper: Helper): Helper by helper

You are using Kotlin's interface delegation. By doing so, you're essentially forwarding the Helper interface's functions to the helper instance. As a result, any public functions defined in the Helper interface can be called directly on an instance of useCase.

Here's an example to clarify:

Suppose the Helper interface looks like this:

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interface Helper {
    fun assist(): String
}

If you have an implementation of Helper:

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class ConcreteHelper : Helper {
    override fun assist() = "Assisting..."
}

And you create useCase like:

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class useCase(helper: Helper) : Helper by helper

Now, when you create an instance of useCase:

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val myUseCase = useCase(ConcreteHelper())

You can directly call:

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println(myUseCase.assist())

This will print "Assisting...".

So, by using interface delegation in this manner, you're effectively exposing the public methods of the helper instance through the useCase class. If you want to hide the Helper's methods or only expose a subset of them, you should avoid using interface delegation in this context.