How to inject WeakReference Fragment using Koin - Android

Question

I have a class that relies on WeakReference<Fragment>.

class ExampleManager(reference: WeakReference<Fragment>) 

How would I inject ExampleManager constructor?

val exampleModule = module {
   factory { ExampleManager(get()) }
}

private val exmpManager: ExampleManager by inject()

At the end I receive error:

No definition found for class:'java.lang.ref.WeakReference'. Check your definitions!

How can I implement definition for WeakReference<Fragment> in my case?

Answer 1

In order to inject a WeakReference using Koin, you can create a factory function that creates the WeakReference and use it in your Koin module definition.

Here's an example:

// Factory function to create WeakReference<Fragment>
fun createWeakRef(fragment: Fragment) = WeakReference(fragment)

// Koin module definition
val exampleModule = module {
    factory { (fragment: Fragment) -> ExampleManager(createWeakRef(fragment)) }
}

Then, you can use the by inject() delegate to inject the ExampleManager class in your activity or fragment:

class ExampleFragment : Fragment() {

    private val exmpManager: ExampleManager by inject { parametersOf(this) }
    // ...
}

Here, parametersOf(this) is used to pass the current fragment instance to the factory function.

It is important to mention that, WeakReference is a java class and you should import it using import java.lang.ref.WeakReference

Make sure you have included the created module in your Koin's startKoin function

i recommend to use'lazy' when you are injecting instances that are only used in certain conditions, this can help to avoid unnecessary instantiation and memory leaks.

private val exmpManager: ExampleManager by inject { parametersOf(this) }.lazy

This way, exmpManager will be instantiated only when it is accessed for the first time.