Step #3: Depositing a Koin

As was noted earlier, Koin can supply ViewModel objects via dependency injection to activities and fragments. However, we have to teach it what ViewModel classes are available for injection.

So, in ToDoApp, modify the koinModule property to add in a viewModel line:

  private val koinModule = module {
    single { ToDoRepository() }
    viewModel { RosterMotor(get()) }
  }

single() is a Koin DSL function that says “make a singleton instance of this object available to those needing it”. viewModel() is a Koin DSL function that says “use the AndroidX ViewModel system to make this ViewModel available to those activities and fragments that need it”. There are a few possible Koin import statements you could have for viewModel() — the one that you want is:

import org.koin.androidx.viewmodel.dsl.viewModel

In our case, we are saying that we are willing to supply instances of RosterMotor to interested activities and fragments. To satisfy the RosterMotor constructor, we use get() to retrieve a ToDoRepository from Koin itself. When it comes time to create an instance of RosterMotor, Koin will get the ToDoRepository singleton and supply it to the RosterMotor constructor.