What is @Named in Kotlin?

Question

The documentation doesn't really help me too much.

I don't understand what it is used for and why it is accompanied by @Inject?

Like in this line

@Named(AUTH_INTENT)
@Inject
lateinit var authIntent: Intent

Answer 1

For most dependencies there is just one class of the requested type in scope (e.g. service implementations), so the instance to inject can be derived from the type.

However if you have multiple objects available for injection (e.g. multiple integer configuration values) you have to add the @Named annotation to specify, which one of the many instances with the same type you want to get.

https://dagger.dev/dev-guide Section: Qualifiers

@Module
class AppModule(val app: Application) {

    @Provides @Named("the_answer")
    fun providesTheAnswer(): Int { 
        return 42
    }

    @Provides @Named("zero")
    fun providesZero(): Int { 
        return 0
    }
}

---

// this works
class MyClass @Inject constructor(
    @Named("the_answer") val answer: Int,
    @Named("zero") val other: Int,
) {
}


// this does not work. Which parameter should get which value?
class MyClass @Inject constructor(
    val answer: Int,
    val other: Int,
) {
}

}