CODEWITHSUNDEEP
androiddependency-injectioncomponentsdagger-2
Nick Titov
Nick Titov

Reputation: 598

Dagger 2 components chain dependencies

I have 3 components: Main app component:

@Singleton
@Component(modules = {AppModule.class, UserModule.class, DatabaseModule.class})
public interface AppComponent {
    Context getContext();

    DatabaseHelper getDatabaseHelper();

    UserManager getUserManager();
}

Repository component:

@DataScope
@Component(dependencies = AppComponent.class, modules = CategoryRepositoryModule.class)
public interface CategoryRepositoryComponent {
    CategoryRepository getCategoryRepository();
}

And screen component:

@MenuScope
@Component(dependencies = CategoryRepositoryComponent.class, modules = {MenuModule.class, DrawerModule.class})
interface MenuComponent {
    void inject(MenuActivity activity);
}

The problem is that my MenuComponent cannot see dependencies that provides AppComponent. But MenuComponent depend on CategoryRepositoryComponent and CategoryRepositoryComponent depend on AppComponent, so MenuComponent should see AppComponent(MenuComponent -> CategoryRepositoryComponent -> AppComponent).

If I will add getters to CategoryRepositoryComponent 

@DataScope
@Component(dependencies = AppComponent.class, modules = CategoryRepositoryModule.class)
public interface CategoryRepositoryComponent {
    CategoryRepository getCategoryRepository();

    DatabaseHelper getDatabaseHelper();

    UserManager getUserManager();
}

But thats looks incorrect, duplicates. Do you know how to resolve this problem in a clean, correct way?

Thanks, Nick.

Upvotes: 3

Views: 1321

Answers (1)

siger
siger

Reputation: 3162

Your approach is correct. Components only have access to the types explicitly exposed by their direct parent component.

This can be useful when, as a parent, you don't want to expose all of your dependencies to whoever depends on you. For example, a Parent may depend on a BankComponent and not want to expose BankAccount to its Children.

An alternative approach is to use Subcomponent. The docs and this other answer will help understand: Dagger 2 subcomponents vs component dependencies.

Upvotes: 4

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