Android - Dagger injection at runtime

Question

i need to inject the class at runtime using dagger. what my problem is am getting compile time error while injecting the class locally in method and also i was not able to inject at runtime without using constant for @Named

Example

interface PerformActionInterface{
      fun performAction()
}

class P1 : PerformActionInterface{
   override fun performAction(){
   }
}

class P2 : PerformActionInterface{
   override fun performAction(){
   }
}


class PerformAction @Inject constructor(){

      fun perform(name : String){

        @Inject
        @Named(name)
        performActionInterface : PerformActionInterface

        performActionInterface.performAction()
    }
}

were as in dagger implementation i will be doing like this

 @Binds
 @Named("p1")
 abstract bindP1Class(p1 : P1) :PerformActionInterface

 @Binds
 @Named("p2")
 abstract bindP1Class(p2 : P2) :PerformActionInterface

Any help for how to inject this at runtime ?

Answer 1

You can't annotate something in runtime, the element value in Java annotation has to be a constant expression.

But this use case can be solved by map multibind.

In your Module, in addition to just @Bind or @Provide, also annotate the abstract fun with @IntoMap and the map key (sorry for any error in my Kotlin)

@Binds
@IntoMap
@StringKey("p1")
abstract fun bindP1Class(p1: P1): PerformActionInterface

@Binds
@IntoMap
@StringKey("p2")
abstract fun bindP2Class(p2: P2): PerformActionInterface

Then in your PerformAction class, declare a dependency of a map from String to PerformActionInterface, and do whatever with the map:

// map value type can be Lazy<> or Provider<> as needed
class PerformAction @Inject constructor(
        val map: Map<String, @JvmSuppressWildcards PerformActionInterface>) {

    fun perform(name: String) {
        map.get(name)?.performAction()
        // or do something if the get returns null
    }
}