what is the correct way of using delegation in the...

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[robstoll]

what is the correct way of using delegation in the context of an object? I tried this but get a compilation error, factory must to be initialized:

object CoreFactory : ICoreFactory by factory {
    private val factory: ICoreFactory

    init {
        val loader = ServiceLoader.load(ICoreFactory::class.java)
        val itr = loader.iterator()
        check(itr.hasNext()) {
            "Could not find an implementation for ${ICoreFactory::class.java.name}"
        }
        factory = itr.next()
    }
}

[orangy]

I would simply use lazy top-level property:

val CoreFactory by lazy {
        val loader = ServiceLoader.load(ICoreFactory::class.java)
        val itr = loader.iterator()
        check(itr.hasNext()) {
            "Could not find an implementation for ${ICoreFactory::class.java.name}"
        }
        itr.next()
}

[robstoll]

I think I would have never come up with this solution, thanks 🙂

[orangy]

Also since ServiceLoader implements Iterable, you might do this:

[orangy]

ServiceLoader.load(ICoreFactory::class.java).firstOrNull() ?: throw IllegalStateException("Could not find an implementation for ${ICoreFactory::class.java.name}")

[orangy]

Or singleOrNull if you want to constraint to only single implementation being available

[robstoll]

actually I do (constrain it to a single implementation), thanks for the additional hint