How can I transform Unit object to DTO object? - kotlin

Question

I am trying to change my code to strategy pattern using spring boot and kotlin, but I can not return my object list in function into Service. How can i transform the output of my forEach which is a Unit to an list of Object DTO which is what my function should actually return? Below are the codes:
interface RecommendationStrategy {
fun validateCorrect(amount: BigDecimal, asset: Asset?, reasonId: Int?): Boolean
fun send(): List<ProductDto>
}
#Component
class StrategyA(
private val serviceHelper: ServiceHelper
) : RecommendationStrategy {
override fun validateCorrect(amount: BigDecimal, asset: Asset?, reasonId: Int?): Boolean {
if (/* logical conditions */) {
return true
}
if (/* logical conditions */) {
return true
}
return false
}
override fun send(): List<ProductDto> {
return serviceHelper.getProducts().filter { it.id!! == 3L || it.id == 1L }
.map { serviceHelper.getlProductMap(it) }.sortedByDescending { it.id }
}
}
#Component
class StrategyB(
private val serviceHelper: ServiceHelper
) : RecommendationStrategy {
override fun validateCorrect(amount: BigDecimal, asset: Asset?, reasonId: Int?): Boolean {
if (/* logical conditions */)) {
return true
}
if (/* logical conditions */) {
return true
}
if (/* logical conditions */) {
return true
}
return false
}
override fun sendLoan(): List<ProductDto> {
return serviceHelper.getProducts().filter { it.id!! == 1L }
.map { serviceHelper.getProductMap(it) }
}
}
#Service
class RecommendationService(
private val recommendationStrategy: List<RecommendationStrategy>,
private val serviceHelper: ServiceHelper
) {
#Transactional(readOnly = true)
fun getProductsRecommended(amount: BigDecimal, asset: Asset?, reasonId: Int?): List<ProductDto> {
val result =
recommendationStrategy.forEach { if (it.validateCorrectLoan(amount, asset, reasonId)) it.send() }
}
}