koin_multibinding.kt

import org.koin.core.Koin
import org.koin.core.context.startKoin
import org.koin.core.module.Module
import org.koin.core.qualifier.Qualifier
import org.koin.core.qualifier.named
import org.koin.dsl.module
import org.koin.dsl.onClose
import org.koin.ext.getFullName

// Based on Koin 3.1.2

@PublishedApi
internal class Multibinding<K, V> : MutableMap<K, V> by mutableMapOf()

inline fun <reified K, reified V> multibindingQualifier(): Qualifier =
    named("${K::class.getFullName()}_${V::class.getFullName()}")

inline fun <reified K, reified V> Module.declareMultibinding() {
    single(qualifier = multibindingQualifier<K, V>()) {
        Multibinding<K, V>()
    }
}

inline fun <reified K, reified V> Module.intoMultibinding(key: K, value: V) {
    var multibinding: Multibinding<K, V>? = null
    single(
        qualifier = named("${K::class.getFullName()}_${V::class.getFullName()}_$key"),
        createdAtStart = true,
    ) {
        multibinding = get(multibindingQualifier<K, V>())
        multibinding!![key] = value
    }.onClose {
        multibinding?.remove(key)
    }
}

inline fun <reified K, reified V> Koin.getMultibinding(): Map<K, V> =
    get<Multibinding<K, V>>(qualifier = multibindingQualifier<K, V>()).toMap()

fun main() {
    val koin = startKoin {
        val module1 = module {
            declareMultibinding<String, Int>()
            intoMultibinding("one", 1)
            intoMultibinding("two", 2)
            intoMultibinding("three", 3)

            declareMultibinding<String, Double>()
            intoMultibinding("one", 1.0)
        }
        val module2 = module {
            intoMultibinding("six", 6)
            intoMultibinding("seven", 7.0)

            declareMultibinding<Float, Unit>()
            intoMultibinding(3.14f, Unit)
        }
        modules(module1, module2)
    }.koin

    println(koin.getMultibinding<String, Int>()) // {one=1, two=2, six=6, three=3}
    println(koin.getMultibinding<String, Double>()) // {seven=7.0, one=1.0}
    println(koin.getMultibinding<Float, Unit>()) // {3.14=kotlin.Unit}

    val module3 = module {
        intoMultibinding("seven", 7)
    }
    koin.loadModules(listOf(module3))
    println(koin.getMultibinding<String, Int>()) // {one=1, two=2, six=6, three=3, seven=7}

    koin.unloadModules(listOf(module3))
    println(koin.getMultibinding<String, Int>()) // {one=1, two=2, six=6, three=3}
}