How to provide arguments like this `Callback` in ...

# dagger

[Kulwinder Singh]

How to provide arguments like this Callback in Fragment using HILT

class PostAdapter @Inject constructor(
    @ApplicationContext private val context: Context,
    private val callback: Callback //HOW THIS CAN BE PROVIDED FROM FRAGMENT
) : ListAdapter<Post, PostAdapter.Holder>(DIFF) {

  /.../

   interface Callback {
        fun onClick(post: Post)
    }

}

[Rafal]

Depends on what that callback does

[Rafal]

Do you want your Fragment to implement this Callback ?

[Javier]

Why do you need the context? You can get the context from the view

[Kulwinder Singh]

@Rafal yes i want to implement it in fragment

[Kulwinder Singh]

@Javier yes, i can skip context but Callback should be implemented by fragment and @Inject using Hilt

[Rafal]

then the only thing I can think of is to make a method that could provide an Optional<Callback> in the fragment scoped module

[Rafal]

@Provides
fun provideCallback(fragment: Fragment): Optional<Callback> = if(fragment is Callback) Optional.of(fragment) else Optional.empty()

[Kulwinder Singh]

@Rafal looks like it would work

[Kulwinder Singh]

but this maybe too much for this case

[Kulwinder Singh]

i am thinking to create Adapter instance manually in fragment

[Rafal]

well, with your constructor arguments this sounds like a better option

[Javier]

I don't think you should use DI for this btw

[ritesh]

+1 to above. You should not use DI for callback.

[dawidhyzy]

@Rafal You don't need to wrap fragment with Optional. You can just bind fragment to Callback type.

@Binds
fun bindCallback(fragment: Fragment): Callback

[Rafal]

how does Dagger will know if the fragment actually implements this Callback

[dawidhyzy]

From this binding

[dawidhyzy]

This the common use of @Binds

[dawidhyzy]

https://dagger.dev/dev-guide/faq.html

[Kulwinder Singh]

@dawidhyzy looks cool, so i don’t have to provide any implementation ?

[Kulwinder Singh]

because @Binds is going to be abstract if i’m not wrong

[Kulwinder Singh]

and it would be better to add parameter fragment more specific like @Rafal You don't need to wrap fragment with Optional. You can just bind fragment to Callback type ???

@Binds
fun bindCallback(fragment: LoginFragment): Callback

[Rafal]

It wont work with hilt because you cant bind concrete fragment instance

[Rafal]

If you install your module inside the FragmentComponent you can only refference the Fragment class

[Rafal]

You will get the error that you cant bind instance from class that doesnt implement given interface

[Rafal]

You could do that in dagger-android