Merge properties of a list to another based on properties objects-CodePudding

I got 2 lists with x objects inside , for example:

data class Model(
    var token: String = "",
    var id: String = "",
    var name: String = "",
    var image: Int = 0,
)

array is initialized and filled, the other list has x objects also that contains the objects of the first list but with different values in their properties!

what I want to do is to change the properties of the first array by the second one if they got the same object.name

var arr1 = ArrayList<Model>() // locale  
var arr2 = ArrayList<Model>() // from db

the first array I got for example

[Model(name = "David", token = "" , image = 0)]

the second array I got

[Model(name = "David", token = "1asd5asdd851", image = 1)]

How do I make the first array take the missing token?

I tried with .filter{} and with .map{}. groupBy {} for hours because Name is the only properties that are the same but I'm more and more confused.

CodePudding user response：

We can first group the second array by name using associateBy() and then iterate over first array and reassign properties:

val arr2ByName = arr2.associateBy { it.name }
arr1.forEach { item1 ->
    arr2ByName[item1.name]?.let { item2 ->
        item1.token = item2.token
        item1.image = item2.image
    }
}

Alternatively, if you don't need to modify items in arr1, but create another array and you can use items from both arr1 and arr2, then it will be much easier:

val arr3 = arr1.map { arr2ByName[it.name] ?: it }

CodePudding user response：

One possible way would be to use fold() as follows:

fun main(args: Array<String>) {
    val arr1 = listOf(Model(name = "David", token = "" , image = 0))
    val arr2 = listOf(Model(name = "David", token = "1asd5asdd851", image = 1))

    val mergedModels = arr2.fold(arr1) { localModels, dbModel ->
        localModels.map { localModel ->
            if (localModel.name == dbModel.name) localModel.copy(token = dbModel.token, image = dbModel.image)
            else localModel
        }
    }

    println(mergedModels)
}

If you want to reuse arr1 variable then you can do the following (but I would still use the previous option):

fun main(args: Array<String>) {
    var arr1 = listOf(Model(name = "David", token = "" , image = 0))
    val arr2 = listOf(Model(name = "David", token = "1asd5asdd851", image = 1))

    arr1 = arr2.fold(arr1) { localModels, dbModel ->
        localModels.map { localModel ->
            if (localModel.name == dbModel.name) localModel.copy(token = dbModel.token, image = dbModel.image)
            else localModel
        }
    }

    println(arr1)
}