pseudo_constructors.kt

// Some (Java) library:

class Context {
    fun register(cl: SomeClient) {
        cl.initClient(this)
    }
}

abstract class SomeClient {
    abstract fun initClient(ctx: Context)
}

// Own program:

class OwnClient: SomeClient() {
    var context: Context? = null
    
    override fun initClient(ctx: Context) {
        context = ctx
    }
    
    fun ownCode() {
        // Better way of handling context?
        if (context == null) {
            // handle this...
        } else {
            // can't just use context, since it is a var, have to use context!! everywhere :(
            println("hello world")
        }
    }
}

fun main(args: Array<String>) {
    val ctx = Context()
    var cl = OwnClient()
    ctx.register(cl)
    cl.ownCode()
}