How to pass in parameters to a dagger module from a activity or fragment at runtime

Question

My software specifications are as follows:

Android Studio 3.4
dagger-android 2.16

I have the following class that passes a MapboxGeocoder that will execute and return a response.

class GeocodingImp(private val mapboxGeocoder: MapboxGeocoder) : Geocoding {

    override fun getCoordinates(address: String, criteria: String): AddressCoordinate {
        val response = mapboxGeocoder.execute()

        return if(response.isSuccess && !response.body().features.isEmpty()) {
            AddressCoordinate(
                response.body().features[0].latitude,
                response.body().features[0].longitude)
        }
        else {
            AddressCoordinate(0.0, 0.0)
        }
    }
}

However, the MapboxGeocoder is generated in a dagger module at compile time. So I have to specify the string for the address and TYPE_ADDRESS.

@Reusable
@Named("address")
@Provides
fun provideAddress(): String = "the address to get coordinates from"

@Reusable
@Provides
@Named("geocoder_criteria")
fun provideGeocoderCriteria(): String = GeocoderCriteria.TYPE_ADDRESS

@Reusable
@Provides
fun provideMapboxGeocoder(@Named("address") address: String, @Named("geocoder_criteria") geocoderCriteria: String): MapboxGeocoder =
    MapboxGeocoder.Builder()
        .setAccessToken("api token")
        .setLocation(address)
        .setType(geocoderCriteria)
        .build()

@Reusable
@Provides
fun provideGeocoding(mapboxGeocoder: MapboxGeocoder): Geocoding =
    GeocodingImp(mapboxGeocoder)

my component class:

interface TMDispatchMobileUIComponent {
    @Component.Builder
    interface Builder {
        @BindsInstance
        fun application(application: TMDispatchMobileUIApplication): Builder

        fun build(): TMDispatchMobileUIComponent
    }

    fun inject(application: TMDispatchMobileUIApplication)
}

In the main activity I would use this like this as the user can enter in a different address or change the criteria to something else. But as the module are compiled I cannot pass any parameters to them at runtime:

presenter.getAddressCoordinates("this should be the actual address", GeocoderCriteria.TYPE_ADDRESS)

For my injection into the Activity I use the following:

AndroidInjection.inject(this)

Is there any solution to this problem?

Answer 1

The problem you have can be solved using "Assisted injection" approach.

It means that you need a class to be built both using dependencies provided from the existing scopes and some dependencies from the instance's creator, in this case, your main activity. Guice from Google has a nice description of what it is and why it is needed

Unfortunately, Dagger 2 does not have this feature out from the box. However, Jake Wharton is working on a separate library that can be attached to Dagger. Moreover, you can find more details in his talk on Droidcon London 2018, where he dedicated a whole talk section for this question: https://jakewharton.com/helping-dagger-help-you/

Answer 2

You can recreate your whole component at runtime if you wish, where you'd then pass in the parameters to your module as a constructor parameter. Something like:

fun changeAddress(address: String) {
    val component = DaggerAppComponent.builder() //Assign this to wherever we want to keep a handle on the component
            .geoModule(GeoModule(address))
            .build()
    component.inject(this) //To reinject dependencies
}

And your module would look like:

@Module
class AppModule(private val address: String) {...}

This method may be wasteful though, if you're creating many different objects in your component.