Injecting Named Dependencies within Constructor

Hello,

Is there a way to inject a named dependency within a constructor? And if not, do you have a recommended way of doing this? Let’s say I have the following:

val myModule = applicationContext {
    bean("A") { MyComponent() } 
    bean("B") { MyComponent() }
    bean { MyOtherComponent() }
}

And I have an object that I is instantiated using constructor injection:

class MyThirdComponent(val componentA: MyComponent, val otherComponent: MyOtherComponent) {
    ...
}

How would I specify which MyComponent I want in the MyThirdComponent constructor? I see in the docs how to specify which named component when injecting directly into other beans but not into a constructor.

I see some potential workarounds:

• Not use construction injection on MyThirdComponent and create a bean instead:

val myModule = applicationContext {
    ...
    bean { MyThirdComponent(get("A"), get()) }
}

It defeats the purpose of constructor injection and requires two maintenance points (if I change the constructor of MyThirdComponent I would need to change the bean instantiation as well), but it could potentially work.

• Inject what I can with the constructor, and then have MyThirdComponent extend KoinComponent and finish off the other injections with by inject:

class MyThirdComponent(val otherComponent: MyOtherComponent) : KoinComponent {
    val componentA: MyComponent by inject("A") 
    ...
}

It’s slightly more tedious but all of the injection is in one place and there’s no need to create an unnecessary bean in this case.

Am I missing something here/is there a better solution? If not, do you have any recommendations/thoughts on the above? I haven’t tested any of these solutions yet, and I just started playing around with Koin today so this might be wrong… My apologies if this has been answered already, I searched the docs / issues and couldn’t find anything on this subject.

Merci! Julien

[saket]

FYI get() was updated and accepts a Qualifier instead of a String. So the new solution would be:

MyOtherComponent(get(named("A")))

[100nandoo]

Hello @jguerinet, avoid using KoinComponent if you can. Try to always use constructor injection.

For you case, just use the name parameter as follow:

val myModule = applicationContext {
    bean("A") { MyComponent() } 
    bean("B") { MyComponent() }
    bean { MyOtherComponent(get("A"),get("B")) }
}

What is the reason behind that? Does using KoinComponent have slower performance? Or maybe slower compile time?