Kotlin Builder Pattern

DialogBuilder.kt

class Dialog private constructor(
        val title: String,
        val message: String,
        val titleColor: Color,
        val bodyColor: Color,
        val icon: Image,
        val onClose: () -> Unit) {

    fun show() {
        //...
    }

    class DialogBuilder {
        val title: String
        val message: String
        var titleColor: Color = Color.RED
        var bodyColor: Color = Color.BLACK
        var icon: Image = Image.info()
        var onClose: () -> Unit = {}

        constructor(title: String, message: String, init: DialogBuilder.() -> Unit) {
            this.title = title
            this.message = message
            init()
        }

        fun build(): Dialog = Dialog(title, message, titleColor, bodyColor, icon, onClose)
    }

    companion object {
        fun build(title: String, message: String, init: DialogBuilder.() -> Unit) =
                DialogBuilder(title, message, init).build()

        fun build(title: String, message: String) = DialogBuilder(title, message, {}).build()
    }
}

fun main(args: Array<String>) {
    val errorDialog = Dialog.build("Uzgunuz", "Beklenmedik bir hata olustu") {
        titleColor = Color.RED
        bodyColor = Color.YELLOW
        icon = Image.error()
    }
    errorDialog.show()

    val infoDialog = Dialog.build("Tebrikler", "Buyuk ikramiye size cikti.") {
        titleColor = Color.GREEN
        icon = Image.info()
    }
    infoDialog.show()
}