Is it possible to have a scoped child component that narrows

Question

Is it possible to have a scoped child component that narrows the scope for a dependency Example in thread

eygraber · Answer

In this example `ChildScreen bar` will be created by getting an instance of `Foo` from the parent component Is there a way to have `ChildScreenComponent` have its own scoped value for `Foo` that is separate from the one in `ParentScreenComponent` ``` Scope annotation class ScreenScope ScreenScope Inject class Foo class ParentScreen private val component = ParentScreenComponent class create private val childScreen by lazy component childScreen ScreenScope Component abstract class ParentScreenComponent abstract val childScreen ChildScreen ScreenScope Provides fun parentComponent = this Inject class Bar foo Foo Inject class ChildScreen private val parentComponent private val childComponent = ChildScreenComponent class create parentComponent private val bar Bar by lazy childComponent bar ScreenScope Component abstract class ChildScreenComponent Component val parentComponent ParentScreenComponent abstract val bar Bar ```

eygraber · Answer

Actually it looks like any child component that uses a scope from the parent component will scope the injections to the parent < evant> is that intentional I ve been working with Kodein the past few years where scoping works very differently so I m having some difficulty

evant · Answer

My assumption would be this would be a compile error to have the child and parent component have the same scope as it s not clear where it should come from It s certainly possible that that check is missing though

eygraber · Answer

Looks like there s no compiler error So the expectation is that if I want each screen using the example from above to have its own scope it would have to have a separate scope annotation And that if I wanted to have a class like `Bar` bound in multiple scopes I should not put the scope or inject annotation on `Bar` itself but define typealiases and do it there

evant · Answer

gt So the expectation is that if I want each screen using the example from above to have its own scope it would have to have a separate scope annotation yes if there s a parent child relationship between the components You are free to share the same scope annotation on sibling components for example gt And that if I wanted to have a class like `Bar` bound in multiple scopes I should not put the scope or inject annotation on `Bar` itself but define typealiases and do it there yeah that would work Basically the scope tells which component holds the dependency You can see how it would be confusing if both child and parent component said they were holding it Much in the same way it is if both child and parent component were to provide the dependency

evant · Answer

I ll double check what dagger does but I m pretty confident is works in the same way

evant · Answer

eygraber · Answer

OK framed that way it makes sense In Kodein the scope is defined by a key i e an object that you use to retrieve the dependency Very different model dizzy face

evant · Answer

created a bug for this <https github com evant kotlin inject issues 180>

eygraber · Answer

So the relevant part for me from the Dagger docs you linked is gt Types with ` Inject` constructors may also be annotated with scope annotations These implicit bindings may be used by any component annotated with that scope or any of its descendant components The scoped instance will be bound in the correct scope When it says bound in the correct scope that means it will be bound by the component that has the scope annotation also just checking but the equivalent of a subcomponent is a component that has a property annotated with ` Component`

evant · Answer

gt When it says bound in the correct scope that means it will be bound by the component that has the scope annotation yep I do eventually want to have our own docs on this but for now been pointing people to dagger as scope concept is the same gt also just checking but the equivalent of a subcomponent is a component that has a property annotated with ` Component` more or less Dagger actually has two ways of declaring a component relationship subcomponents and component dependencies kotlin inject s ends up being a hybrid of the two

eygraber · Answer

OK thanks that s helpful to know