ContributesSubcomponent

Similar to MergeSubcomponent, but with the main difference that the subcomponent is generated and modules, bindings and component interfaces are merged whenever the component with parentScope is processed.

Imagine this module dependency tree:

         :app
        /     \
       v       v
    :lib-a   :lib-b

:app creates the component with @MergeComponent, :lib-a creates a subcomponent with @MergeSubcomponent and :lib-b contributes a module to the scope of the subcomponent. This module won't be included in the subcomponent without adding the dependency :lib-a -> :lib-b. See MergeSubcomponent for further explanation.

On the other hand, if :lib-a uses @ContributesSubcomponent with a parent scope of the main component from :app, then the actual subcomponent will be generated in the :app module and the contributed module from :lib-b will be picked up.

@ContributesSubcomponent(
  scope = ActivityScope::class,
  parentScope = AppScope::class
)
interface ActivitySubcomponent

parentScope can be the scope of a MergeComponent, MergeSubcomponent or another ContributesSubcomponent. A chain of ContributesSubcomponents is supported.

It's possible to exclude any automatically added Dagger module or component interface with the exclude parameter if needed.

@ContributesSubcomponent(
  scope = ActivityScope::class,
  parentScope = AppScope::class,
  exclude = [
    DaggerModule::class,
    ComponentInterface::class
  ]
)
interface ActivitySubcomponent

It's recommended to define a parent component interface as inner class of the contributed subcomponent that is contributed to the parent scope. Anvil will always generate a parent component interface for the final generated subcomponent with an abstract factory method for the subcomponent. If you create your own parent component interface, then the one generated by Anvil will extend your interface. E.g.

@ContributesSubcomponent(
  scope = ActivityScope::class,
  parentScope = AppScope::class
)
interface ActivitySubcomponent {

  @ContributesTo(AppScope::class)
  interface ParentComponent {
    fun createActivitySubcomponent(): ActivitySubcomponent
  }
}