Dagger2 component with more than one dependencies

Question

This is what I currently have and it works:

@FragmentScope
@Component(dependencies = {FacebookComponent.class}, 
            


        

Answer 1

You can't use scoped components in a dependencies array (which is quite strange I have to say), only unscoped, or one scoped + other unscoped. But you can deceive dagger with "proxy" interfaces:

@Component
@Singleton
interface ComponentA {
    fun provideSomeA()
}

interface ProxyComponentA : ComponentA

@Component
@Singleton
interface ComponentB {
    fun provideSomeB()
}

interface ProxyComponentB : ComponentB

@Component(dependencies = [ProxyComponentA::class, ProxyComponentB::class])
@OtherScope
interface ComponentC

But in your ComponentC builder you should use proxy components implementations, which could easily be achieved with Kotlin:

class ProxyComponentAImpl(private val delegate: ComponentA) : ProxyComponentA, ComponentA by delegate
class ProxyComponentBImpl(private val delegate: ComponentB) : ProxyComponentB, ComponentB by delegate

componentA = DaggerComponentA.builder()...
componentB = DaggerComponentB.builder()...

componentC = DaggerComponentC.builder()
                   .componentA(ProxyComponentAImpl(componentA))
                   .componentB(ProxyComponentBImpl(componentB))

Works on dagger version 2.13, don't know about others

Also you could use vice versa inheritance ComponentA : ProxyComponentA to eliminate the need to create ProxyComponentAImpl, but it's not a good design choice if your ComponentA lays for example in a different gradle module

The solution was inspired by that issue discussion: https://github.com/google/dagger/issues/1225