I have this dependency:
@Singleton
class SpiceMix @Inject constructor(@field:[Named("oregano")] private val oregano: Spice,
@field:[Named("sage")] private val sage: Spice,
@field:[Named("rosemary")] private val rosemary: Spice)
And a module to fulfill its dependencies:
@Module
class SpiceModule {
@Provides
@Named("oregano")
@Singleton
fun provideOregano(): Spice = Oregano()
@Provides
@Named("sage")
@Singleton
fun provideSage(): Spice = Sage()
@Provides
@Named("rosemary")
@Singleton
fun provideRosemary(): Spice = Rosemary()
The SpiceMix
is then injected in various locations of my app.
However, this does not compile and I get an error:
Spice cannot be provided without an @Provides-annotated method
I think the @Named annotations do not quite work in my constructor signature. I am not quite sure how I can make it work.
Note: this compiles fine if I ditch the Named annotations and change the types of the constructor parameters to their concrete forms. However, Spice is an interface, and I need it for mocking purposes in my tests.
What can I do?
You want to annotate the constructor parameters if you're doing constructor injection, and not the fields - use the @param:
annotation target:
@Singleton
class SpiceMix @Inject constructor(@param:Named("oregano") private val oregano: Spice,
@param:Named("sage") private val sage: Spice,
@param:Named("rosemary") private val rosemary: Spice)
Edit: actually, since the resolution order for annotation targets is
- param;
- property;
- field.
according to the docs, having no annotation target should also annotate the parameter of the constructor. So you can just drop the target altogether:
@Singleton
class SpiceMix @Inject constructor(@Named("oregano") private val oregano: Spice,
@Named("sage") private val sage: Spice,
@Named("rosemary") private val rosemary: Spice)