Can I do anything in this snippet to prevent the need from using a generic and passing in the `Class...

# announcements

[william]

Can I do anything in this snippet to prevent the need from using a generic and passing in the Class as well?

abstract class BaseViewModelFragment<T : ViewModel>(private val type: Class<T>) : BaseInjectedFragment() {
    @Inject
    lateinit var viewModelFactory: ViewModelProvider.Factory
    private lateinit var viewModel: T

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProviders.of(this, viewModelFactory).get(type)
    }
}

[william]

i understand type erasure is a problem here i just don't now if there are other workarounds

[wbertan]

I don't know if it actually works: https://stackoverflow.com/questions/34122450/how-to-get-generic-parameter-class-in-kotlin
Last comment

[wbertan]

It suggests something like:

abstract class BaseViewModelFragment<T : ViewModel> : Fragment() {
    lateinit var viewModelFactory: ViewModelProvider.Factory
    private lateinit var viewModel: T

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProviders.of(this, viewModelFactory).get(
            (this.javaClass
                .genericSuperclass as ParameterizedType)
                .actualTypeArguments[0] as Class<T>
        )
    }
}

[william]

that must be reflection? haven't touched that before but im assuming so

[william]

is this a moment where its ok to use reflection? definately winds up with a cleaner result

[wbertan]

I would not use like that, would explore and perhaps change to not need it.

[william]

how so @wbertan?

[wbertan]

Good question...

[wbertan]

Hey, again, I didn't tested:

abstract class BaseViewModelFragment<T : ViewModel> : Fragment() {
    lateinit var viewModelFactory: ViewModelProvider.Factory
    private lateinit var viewModel: T

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
        viewModel = ViewModelProviders.of(this, viewModelFactory).get(viewModel::class.java)
    }
}

[wbertan]

👀

[william]

holy

[william]

hmmmmmmmmmm

[wbertan]

Check this:

bstract class BaseViewModelFragment<T : ViewModel> : Fragment() {
    lateinit var viewModelFactory: ViewModelProvider.Factory
    abstract val viewModel: T

    inline fun <reified K : ViewModel> asasMagic() = ViewModelProviders.of(this, viewModelFactory).get(K::class.java)

    override fun onViewCreated(view: View, savedInstanceState: Bundle?) {
        super.onViewCreated(view, savedInstanceState)
    }
}

class OtherViewModelFragment: BaseViewModelFragment<ViewModel>() {
    override val viewModel: ViewModel
        get() = asasMagic()
}

[william]

so that definately makes sense using reified just not as abstracted away with having to get the viewmodel

[william]

i think your other solution does work though as this snippet

fun main() {
    Fuzz(3.0)
}

class Fuzz<T : Number>(init: T) {
    init {
        println(init::class.java)
    }
}

prints class java.lang.Double

[Stephan Schroeder]

are reified generics in inline methods methods a possibility? (first and only thought, I didn’t really look at the problem in depth)

[william]

wound up doing this

abstract class BaseViewModelFragment : BaseInjectedFragment() {
    @Inject
    lateinit var viewModelFactory: ViewModelProvider.Factory

    /**
     * Lazily get the view model
     */
    inline fun <reified VM : ViewModel> viewModel() = lazy {
        ViewModelProviders.of(this, viewModelFactory).get(VM::class.java)
    }
}

[william]

so yeah basically the last thing recomended by you guys @Stephan Schroeder @wbertan

[william]

and then in my fragments that extend BaseViewModelFragment I use private val viewModel: HomeViewModel by viewModel()