Kotlin compare two lists - if ids match overwrite it-CodePudding

I have two lists of Object. Both objects have an id val. I need to check both lists by the id val, if the id is the same take the object from list B and overwrite it in list A. Is there a simple up to date way to achieve this outcome in kotlin?

Ive been searching through the kotlin docs and other comparing list questions on here but I havent found anything in the docs or on here that matches my usecase

CodePudding user response：

Not sure about how efficient this is but it works...

Sample Class

data class SomeClass(val id: Int, val someString: String) {

}

fun transformList(firstList: List<SomeClass>, secondList: List<SomeClass>): List<SomeClass> {
    return firstList.map { firstClass ->
        val tempItem = secondList.firstOrNull { it.id == firstClass.id }
        tempItem ?: firstClass
    }
}

basically, the function takes both the lists and compares each item with each other, and returns items from list 2 if the id is the same.

fun main() {

    val listOne = listOf<SomeClass>(
        SomeClass(0, "I am 0, from list 1"),
        SomeClass(1, "I am 1, from list 1"),
    )

    val listTwo = listOf<SomeClass>(
        SomeClass(0, "I am 0, from list 2"),
        SomeClass(1, "I am 1, from list 2"),
    )

    println(transformList(listOne, listTwo))

}

Output

 [SomeClass(id=0, someString=I am 0, from list 2), SomeClass(id=1, someString=I am 1, from list 2)]