Type inference failed while attempting to inject ViewModel

[caleb-allen]

I believe I have followed the docs correctly, but I can't seem to get this working.

I have an activity:

class LoginActivity : BaseActivity() {
    val viewModel: LoginViewModel by getViewModel()
. . .

And I am instantiating my module in my Application class:

val myModule : Module = applicationContext {
            . . . .
            viewModel { MyViewModel(get()) }
}
startKoin(this, listOf(myModule))

but I'm getting a compile error on the by getViewModel() line:

Type inference failed: Not enough information to infer parameter T in intline fun <reified T : ViewModel> FragmentActivity.getViewModel(): T
Please specify it explicitly

If I attempt to specify it via getViewModel<MyViewModel>(), I get this compile error:

Missing 'getValue(MyActivity, KPropery<*>)' method on delegate of type 'MyViewModel'

Or if I try:

val viewModel = getViewModel<LoginViewModel>()

I get a runtime NPE when the ViewModel can't get any instance correctly:

Caused by: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.app.Application.registerActivityLifecycleCallbacks(android.app.Application$ActivityLifecycleCallbacks)' on a null object reference
                                                       at android.arch.lifecycle.HolderFragment$HolderFragmentManager.holderFragmentFor(HolderFragment.java:169)
                                                       at android.arch.lifecycle.HolderFragment.holderFragmentFor(HolderFragment.java:84)
                                                       at android.arch.lifecycle.ViewModelStores.of(ViewModelStores.java:47)
                                                       at example.MyActivity.<init>(LoginActivity.kt:45)
                                                       at java.lang.Class.newInstance(Native Method)
                                                       at android.app.Instrumentation.newActivity(Instrumentation.java:1174)
                                                       at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2669)

Any insights would be greatly appreciated!

[arnaudgiuliani]

Hello,

the delegate form of getViewModel() is by viewModel()

Replace your declaration in your LoginActivity with :
val viewModel: LoginViewModel by viewModel()

If you want to write the val viewModel = getViewModel<LoginViewModel>(), you must use it in the onCreate function.

Tell me if it fixes your situation.

[fredy-mederos]

In the README file there are a little mistake.

// Bind it to your Activity
class MyActivity() : AppCompatActivity() {

  val viewModel : MyViewModel by getViewModel()

  override fun onCreate(){
    super.onCreate()
  }
}

Should be by viewModel()

[arnaudgiuliani]

Just fixed it. Thanks !

[caleb-allen]

This was the correct solution, using by viewModel() rather than by getViewModel(). Thanks!