Add initialState to MvRxFactory, give access to args in create ViewModel #169
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@@ -4,26 +4,92 @@ import android.support.v4.app.Fragment | |
| import android.support.v4.app.FragmentActivity | ||
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| /** | ||
| * Implement this on your ViewModel's companion object for hooks into state creation and ViewModel creation. For example, if you need access | ||
| * to the fragment or activity owner for dependency injection. | ||
| */ | ||
| interface MvRxViewModelFactory<VM : BaseMvRxViewModel<S>, S : MvRxState> { | ||
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| /** | ||
| * @param viewModelContext [ViewModelContext] which contains the ViewModel owner and arguments. | ||
| * @param state The initial state to pass to the ViewModel. In a new process, state will have all [PersistState] annotated members restored, | ||
| * therefore you should never create a custom state in this method. To customize the initial state, override [initialState]. | ||
| * | ||
| * @return The ViewModel. If you return `null` the ViewModel must have a single argument | ||
| * constructor only taking the initial state. | ||
| */ | ||
| fun create(viewModelContext: ViewModelContext, state: S): VM? = null | ||
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There was a problem hiding this comment. The issue I ran into with having a single create in #148 was casting. If the consumer wants the For me, cause Dagger injects the There was a problem hiding this comment. @marukami Yeah, that is a downside, but I don't see a safe way around this. It seems too risky to have a ViewModelFactory that will crash if you use an activity scope. I think, if in your application you know that you will only use fragment scoped view models, you could do something like: That way you are explicitly performing the unsafe cast. Does this seem reasonable? There was a problem hiding this comment. With the changes @gpeal suggested for the Fragment been a generic, I think an extension function like this should work nicely. @Suppress("UNCHECKED_CAST")
inline fun <F: Fragment> ViewModelContext.withFragmentFactory(factory: (F) -> ViewModel) =
(this as FragmentViewModelContext).let { it.fragment as F }.let(factory) |
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| /** | ||
| * The initial state for the ViewModel. Override this if the initial state requires information from arguments, or the ViewModel owner. | ||
| * This function will take precedence over any secondary constructors defined in the state class, [S]. | ||
| * | ||
| * The return value of this function will be transformed with any [PersistState] values before being used in [create]. | ||
| * | ||
| * @return the initial state. If `null`, the state class constructors will be used for initial state creation. | ||
| */ | ||
| fun initialState(viewModelContext: ViewModelContext): S? = null | ||
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| } | ||
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| /** | ||
| * Creation context for the ViewModel. Includes the ViewModel store owner (either an activity or fragment), and fragment arguments | ||
| * set via [MvRx.KEY_ARG]. | ||
| * | ||
| * For activity scoped ViewModels see [ActivityViewModelContext]. | ||
| * For fragment scoped ViewModels see [FragmentViewModelContext]. | ||
| * | ||
| * Never store a reference to this context, or the activity/fragment. | ||
| * | ||
| */ | ||
| sealed class ViewModelContext { | ||
| /** | ||
| * The activity which is using the ViewModel. | ||
| */ | ||
| abstract val activity: FragmentActivity | ||
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| /** | ||
| * Convenience method to type [activity]. | ||
| */ | ||
| @Suppress("UNCHECKED_CAST") | ||
| fun <A : FragmentActivity> activity() : A = activity as A | ||
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| /** | ||
| * Fragment arguments set via [MvRx.KEY_ARG]. | ||
| */ | ||
| abstract val args: Any? | ||
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| /** | ||
| * Convenience method to type [args]. | ||
| */ | ||
| @Suppress("UNCHECKED_CAST") | ||
| fun <A> args(): A = args as A | ||
| } | ||
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| /** | ||
| * The [ViewModelContext] for a ViewModel created with an activity scope (`val viewModel by activityViewModel<MyViewModel>`). Although a fragment | ||
| * reference is available when an activity scoped ViewModel is first created, during process restoration, activity scoped ViewModels will be created | ||
| * _without_ a fragment reference, so it is only safe to reference the activity. | ||
| */ | ||
| class ActivityViewModelContext( | ||
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There was a problem hiding this comment. It's not immediately clear to me why we need to separate fragment and activity contexts, since an activity scoped viewmodel is still initially created for a specific fragment, and with arguments from that fragment. I suppose it's just during process restart that we don't have the original fragment anymore? That's subtlety makes this requirement/distinction not immediately clear There was a problem hiding this comment. Fragment access is needed for simple Dagger support. With access to the fragment, all you need to do is inject a ViewModel factory. With #148 I just forward the MvRx factory invoke to the dagger injected factory in the fragment. There was a problem hiding this comment. @elihart Yes, during process activity scoped ViewModels will be recreated when the activity is created. So even in a normal creation sequence we will pass it only the activity (even though a fragment reference is technically accessible). |
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| override val activity: FragmentActivity, | ||
| override val args: Any? | ||
| ) : ViewModelContext() | ||
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| /** | ||
| * The [ViewModelContext] for a ViewModel created with a | ||
| * fragment scope (`val viewModel by fragmentViewModel<MyViewModel>`). | ||
| */ | ||
| class FragmentViewModelContext( | ||
| override val activity: FragmentActivity, | ||
| override val args: Any?, | ||
| /** | ||
| * The fragment owner of the ViewModel. | ||
| */ | ||
| val fragment: Fragment | ||
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There was a problem hiding this comment. @BenSchwab You could make a |
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| ) : ViewModelContext() { | ||
| /** | ||
| * Convenience method to type [fragment]. | ||
| */ | ||
| @Suppress("UNCHECKED_CAST") | ||
| fun <F : Fragment> fragment() : F = fragment as F | ||
| } | ||
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@BenSchwab
@RestrictTo(Library)