Singleton with parameter in Kotlin

Question

I am trying to convert an Android app from Java to Kotlin. There are a few singletons in the app. I used a companion object for the singletons without constructor parameters

Answer 1

solution with lazy

class LateInitLazy(private var initializer: (() -> T)? = null) {

    val lazy = lazy { checkNotNull(initializer) { "lazy not initialized" }() }

    fun initOnce(factory: () -> T) {
        initializer = factory
        lazy.value
        initializer = null
    }
}

val myProxy = LateInitLazy()
val myValue by myProxy.lazy

println(myValue) // error: java.lang.IllegalStateException: lazy not inited

myProxy.initOnce { "Hello World" }
println(myValue) // OK: output Hello World

myProxy.initOnce { "Never changed" } // no effect
println(myValue) // OK: output Hello World