ViewModelFactory.kt

package com.marcellogalhardo.viewmodel.factory

import androidx.fragment.app.viewModels
import androidx.lifecycle.ViewModel
import androidx.lifecycle.ViewModelProvider
import javax.inject.Inject
import javax.inject.Provider

/**
 * A [ViewModelProvider.Factory] that can hold a ViewModel [producer] function
 * to be used with [ViewModelProvider] and [viewModels].
 *
 * When using the [Inject] constructor with Dagger, it will automatically
 * get a [Provider] for the [VM] available in your current scope.
 */
class ViewModelFactory<VM : ViewModel> constructor(
    private val producer: () -> VM
) : ViewModelProvider.Factory {

    /**
     * An internal constructor to be used when injecting with Dagger.
     */
    @Inject
    internal constructor(provider: Provider<VM>) : this(provider::get)

    @Suppress("UNCHECKED_CAST")
    override fun <VM : ViewModel?> create(modelClass: Class<VM>): VM {
        return producer() as? VM
            ?: error("${modelClass.name} cannot be provided without an @Inject constructor or from a @Provides-annotated method.")
    }
}