Dagger: How can I create only one instance of object for each sub component ?

[RobertApikyan]

How can I create only one instance of object for each sub component ?
I use dagger android, I have this scopes
AppScope
ActiivtyScope
FragmentScope
Lets say I have an activity with two fragments, how can I create a new instance of X object for my Activity and for each of fragments separately ?

[tbroyer]

I'm not familiar with them, but maybe @Reusable scope?

[RobertApikyan]

The @Reusable scope will create instance of X object for @AppScope and provide the same instance for @ActivityScope and for @FragmentScope, seance they are Sub Component scopes ( AppComponent -> XActivitySubComponent -> XFragmentSubcomponent ), I mean the same instance will be injected for Activity and Fragment, @Reusable is not solve the problem, thanks for answer

[ronshapiro]

If you define your own scope and apply it to a subcomponent, any binding with that scope will achieve what you're searching to do.

Example:

@Scope
@interface RobertScope {}

@RobertScope
@Subcomponent(modules = RobertModule.class)
interface ActivitySubcomponent {
  ActivityScopedObject a();
}

@Module
class RobertModule {
  @Provides
  @RobertScope
  ActivityScopedObject a() {
   return ... 
  }
}

@tbroyer @Reusable _may_ be shifted down the component tree if it is unused in the parent that defines it, but if you _need_ specific characteristics, a regular scope is the way to go.

[RobertApikyan]

Thanks for answer

But I think you got my question wrong, let me formulate it in another way:

I want to create and reuse the created instances in each sub component, for more details please see attached image, thank you in advance for you feedback

[ronshapiro]

Yup, that's what happens. Every time a new instance of a component is created, it has it's own new set of scoped bindings.

[RobertApikyan]

But in this case what is my instance's scope ?

1. if it is annotated with @FragmentScope the compilation will fail, because my activity is in the @ActivityScope but the instance I want to inject is annotates @FragmentScope).
2. if the instance is annotated with @ActivityScope
   , than it will be shared for Fragment1 and Fragment2, since they are sub components for activity component

[ronshapiro]

Oh, you want _one_ binding that will have a separate instance for each of them? There's no built-in way to do that.

You could probably hack something together with Map multibindings, i.e. Map<Class<? extends Annotation> /* scope class */, YourBinding> if you want.

[RobertApikyan]

Yes, you understand the issue correctly, I solve the issue, and put the fragmens and activities under one single scope, @Screen scope, and they are both subcomponents for the @AppScope

[JonathanMerritt]

@RobertApikyan

Have you tried composing your objects? Based on your scope hierarchy.

[RobertApikyan]

Yes, Shure. But I need to bind a new object to every sub scope, this I think is an injection pattern

[JonathanMerritt]

Not sure if I understand totally...

This is what I mean, at least one way of doing it.

abstract class BaseType<T extends BaseType> {
  final T type;

  BaseType(T type){ this.type = type; }
}

@AppScope class AppType extends BaseType {
  @Inject AppType(){  super(null); }

  void appThing(){}
}

@ActivityScope class ActivityType extends BaseType<AppType> {
  @Inject ActivityType(AppType type){ super(type); }

  void appThing(){ type.appThing(); }

  void activityThing(){}
}

@FragmentScope class FragmentType extends BaseType<ActivityType> {
  @Inject FragmentType(ActivityType type){ super(type); }

  void appThing(){ type.appThing(); }

  void activityThing(){ type.activityThing(); }

  void fragmentThing(){}
}

Probably more then you would want to do. But it's not too bad as long as you don't have a large amount of scopes.

[RobertApikyan]

thanks for the example,
But I think you got my question wrong.
Imagine the situation when my activityComponent (@ActivityScope) is subcomponent for the appComponent(@AppScope) and the fragmentComponent(@FragmentScope) is the subComponent for the activityComponent.
I have an HomeActivity which contains two fragments, with specified scopes ( StatisticsFragment and the RequestsFragment)
Now I need to create a new instance of some object (lets call it X object) one for my HomeActivity, one for StatisticsFragment and one for RequestsFragment and reuse thins objects, I mean if I already have created this object for my RequestsFragment I want to reuse it for RequestsFragmentPresenter and for RequestsRepository, and the same behevior for HomeActivity and StatisticsFragment.
Now the problem is that when I create the instance of X object for my HomeActivity, it passes the same created object from HomeActiviy to RequestsFragment and StatisticsFragment.

1. if X is annotated with @FragmentScope the compilation will fail, because my activity is in the @ActivityScope but the instance I want to inject is annotates @FragmentScope).
2. if the X instance is annotated with @ActivityScope
   , than it will be shared for Fragment1 and Fragment2, since they are sub components for activity component

You can see the diagram here

[JonathanMerritt]

Ah, I think I understand now. Actually sounds like it's more of an Activity/Fragment lifecycle issue, not injection.

I'm guessing you'd want the object cleared when its supplying activity or fragment is destroyed etc...

[RobertApikyan]

Not so close, the issue is to create new Instance of X object once for every sub scope, and reuse the instance in its scope, for HomeActivity and for 2 child fragments I need 3 new instances of X object

[JonathanMerritt]

Sorry I couldn't help.

I hope you get something figured out.

[RobertApikyan]

it's Ok,
Thank you
I solve the issue, and put the fragmens and activities under one single scope, @screen scope, and they are both subcomponents for the @AppScope

[Badranh]

@RobertApikyan Hello Robert, I'm stuck in the same problem you had before so please can you tell me in details how you managed it ?

[RobertApikyan]

Hi, sorry for late answer ... 

Вторник, 30 апреля 2019, 21:53 +04:00 от Hasan Badran [e-mail]:

@RobertApikyan Hello Robert, I'm stuck in the same problem you had before so please can you tell me in details how you managed it ?
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You are receiving this because you were mentioned.
Reply to this email directly, view it on GitHub , or mute the thread .

С уважением,
Robert Apikyan
[email protected]

[RobertApikyan]

If you want to have different instances in the Component and in it's Sub-components, The problem can not be resolved, dagger do not support such a dependency schema, 

I have crated the custom Scope ( @ScreenScope ) and applied it to my activity and to it's child fragments, so now the activity and it's child fragments do not share any objects, 
not a perfect solution it, but this was the only one for that time ... To be honest now i'm trying to avoid using of dagger in my projects, overall it's a good library,  but in this common case it does not provide valid solution ... 

Четверг, 2 мая 2019, 13:19 +04:00 от Robert Apikyan [e-mail]:

Hi, sorry for late answer ... 

Вторник, 30 апреля 2019, 21:53 +04:00 от Hasan Badran < [email protected] >:

@RobertApikyan Hello Robert, I'm stuck in the same problem you had before so please can you tell me in details how you managed it ?
—
You are receiving this because you were mentioned.
Reply to this email directly, view it on GitHub , or mute the thread .

С уважением,
Robert Apikyan
[email protected]

С уважением,
Robert Apikyan
[email protected]

[Badranh]

@RobertApikyan Thanks man!