比较Kotlin中的两个对象

我刚刚开始学习 Kotlin。我有两个对象，我需要比较它们。我只想要更改名称的汽车列表（我想在数据库中使用新值更新车库对象，当它更改时）

对象一：

{
    "name": "Tom's garage"
    "brands": [
        {
            "name": „Volkswagen”,
            "cars": [
                {
                    "id": „1”,
                    „name”: „Golf”
                },
                {
                    "id": „2”,
                    „name”: „Tiguan”
                }
            ]
        },
        {
            "name": „Audi”,
            "cars": [
                {
                    "id": „3”,
                    „name”: „A3”
                },
                {
                    "id": „4”,
                    „name”: „A4”
                }
            ]
        }
    ]
}

对象二：

{
    "name": "Tom's garage"
    "brands": [
        {
            "name": „Volkswagen”,
            "cars": [
                {
                    "id": „1”,
                    „name”: „Golf”
                },
            ]
        },
       {
            "name": „Audi”,
            "cars": [
                {
                    "id": „3”,
                    „name”: „A5””
                },
            ]
        }
    ]
}

所以在输出中，我只想要车库中更名的汽车列表（奥迪 A3 到奥迪 A5）。

[
       {
            "name": „Audi”,
            "cars": [
                {
                    "id": „3”,
                    „name”: „A5””
                },
            ]
        }
]

这就是我写的，但我对我的代码不满意。你能建议我更好的 kotlin 解决方案吗？

    fun findDiff(current: Garage, updated: Garage): List<Car> {
        val carsMap = current.brands.map {
                brand -> brand.name to brand.cars.map { car -> car.id to car }.toMap()
        }.toMap()

        val output = arrayListOf<Car>()

        for (brand in updated.brands) {
            for (car in brand.cars) {
                currentSettingsMap[brand.name]?.get(car.id)?.
                let { currentCar ->
                    if (currentCar.name != car.name) {
                        output.add(car)
                    }
                }
            }
        }
        
        return output
    }

模型：

class Garage(
    val name: String
    val brands: List<Brand> = emptyList()
)

class Brand(
    val name: String,
    val cars: List<Car> = emptyList()
)

class Car(
    val id: Int,
    val name: String
)

这是学习的例子，没有任何意义。

回答

fun findDiff(current: Garage, updated: Garage): List<Car> {
    // preparing a map for fast search
    val currentCars = current.brands
        .flatMap { it.cars }    // list of all cars in "current" garage
        .associateBy { it.id }  // car.id -> car

    return updated.brands.asSequence()
        .flatMap { it.cars }                // list of all cars in "updated" garage
        .filter { it.id in currentCars }    // we remove cars that are not in the "current" garage
        .filter { it.name != currentCars.getValue(it.id).name } // filtering cars with the same id and different names
        .toList()
}