CODEWITHSUNDEEP
androidkotlin
Valentin
Valentin

Reputation: 1741

Kotlin - declare a generic class with a type param which is generic

So I have a BasePresenter class like so. BaseMvpView is an interface

open class BaseMvpPresenter<View : BaseMvpView> {
}

I am trying to create a BaseMvpActivity class which is parameterized with a BaseMvpPresenter like so:

abstract class BaseMvpActivity<T : BaseMvpPresenter> : BaseActivity(), BaseMvpView {
}

But I get the following error: 

One type argument expected for class BaseMvpPresenter<View: BaseMvpView>

How do I properly declare this? I want to be able to use BaseMvpActivity as so:

abstract class BaseMvpActivity<T : BaseMvpPresenter<U>, U : BaseMvpView> : BaseActivity(), BaseMvpView {

    abstract var presenter: T

    override fun onCreate(savedInstanceState: Bundle?) {
        super.onCreate(savedInstanceState)
        presenter.onViewCreated(this)
    }

    override fun onDestroy() {
        presenter.onViewDestroyed()
        super.onDestroy()
    }
}

Upvotes: 3

Views: 2533

Answers (1)

Jefferson Tavares
Jefferson Tavares

Reputation: 991

You need to pass the parameter to the BaseMVPPresenter. You can add a second parameter to your abstract class as follows

abstract class BaseMvpActivity<V: BaseMvpView, T : BaseMvpPresenter<V>> : BaseActivity(), BaseMvpView {
}

so lets say you're creating a view to show posts, then you would do something like this: 

class Activity : BaseMVPActivity<PostsView, PostPresenter<PostView>() {
    //Here comes your code
}

Hope this helps :)

Upvotes: 4

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