How to call method Reference in map - kotlin

Question

I create a class ApUtils . Define two methods in that class . I want
use that two methods in my service class inside the map function by
the help of method reference ,But I am getting un excepted error while
calling these two methods
service.kt
package com.nilmani.reactivespringdemo.services
import com.nilmani.reactivespringdemo.Utils.AppUtils
import com.nilmani.reactivespringdemo.dto.ProductDto
import com.nilmani.reactivespringdemo.entity.Product
import com.nilmani.reactivespringdemo.repository.ProductRepository
import org.springframework.beans.factory.annotation.Autowired
import org.springframework.stereotype.Service
import reactor.core.publisher.Flux
import reactor.core.publisher.Mono
#Service
class ProductService {
#Autowired
private lateinit var productRepository: ProductRepository
fun getProduct():Flux<ProductDto>{
return productRepository.findAll().map(obj: AppUtils -> obj.entityToDto(product))
}
fun getProduct(id:String):Mono<ProductDto>{
return productRepository.findById(id).map{ obj: AppUtils, product: Product -> obj.entityToDto(product) }
}
}
AppUtils.kt
package com.nilmani.reactivespringdemo.Utils
import com.nilmani.reactivespringdemo.dto.ProductDto
import com.nilmani.reactivespringdemo.entity.Product
import org.springframework.beans.BeanUtils
class AppUtils {
fun entityToDto(product: Product):ProductDto{
val productDto = ProductDto()
BeanUtils.copyProperties(product,productDto)
return productDto
}
fun dtoToEntity(productDto: ProductDto):Product{
val product = Product()
BeanUtils.copyProperties(productDto,product)
return product
}
}
How to call these two function in my service class using method reference

Answer 1

If you change AppUtils to a singleton using Kotlin's object keyword:
object AppUtils { ... }
then you can use method references like so:
fun getProduct(id:String) = productRepository.findById(id).map(AppUtils::entityToDto)