Kotlin Convert Genertic Class to Map-CodePudding

there is a A Data Class

data class A(val x: String?, val y: Int?)

and I have to one two and if there're null value in one then replace it two's property value but if not null then remain one's value

val one = A(null, 3) 
val two = A("11", 4)

A("11", 3)

The idea I came up with is convert two A object to Map and merge two Map and then deserialize merged Map to A

My question is

is there any best idea merge two object?(My Situation)
How to convert Generic Class To Map

inline fun <reified T> toJsonObject(value: T): Map<String, Any> =
        objectMapper.readValue(objectMapper.writeValueAsString(value), Map::class.java)

this does not working please help me..

CodePudding user response：

This is possible only with reflection:

import kotlin.reflect.full.declaredMembers
   
inline fun <reified T> T.takeValuesIfNullFrom(item: T): T {
  if(this!!::class != item!!::class) return this
  val constructor = T::class.constructors.first()
  val parameterNames = constructor.parameters.map { parameter -> parameter.name }
  val arguments = T::class.declaredMembers
    .filter { it.name in parameterNames }
    .map { it.call(if (it.call(this) == null) item else this) }
  return constructor.call(*arguments.toTypedArray())
}

Test:

data class A(val x: String?, val y: Int?)

val one = A(null, 3)
val two = A("11", 4)

data class B(val x: String?, val y: Int?, val z: Float?)

val three = B(null, 5, null)
val four = B("22", 6, 123.456f)

val resultA = one.takeValuesIfNullFrom(two)
println(resultA)

val resultB = three.takeValuesIfNullFrom(four)
println(resultB)

Output:

A(x=11, y=3)
B(x=22, y=5, z=123.456)