CODEWITHSUNDEEP
algorithmkotlin
happycoder
happycoder

Reputation: 3

Comparation two objects in Kotlin

I have just started to learn Kotlin. I have two objects and I need to compare them. I only want list of cars with changed name (I want to do update garage object in database with new value when it's changed)

Object one:

{
    "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”
                }
            ]
        }
    ]
}

Object two:

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

So in output I want only list of cars with changed name (Audi A3 to Audi A5) in the garage.

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

That's what I wrote, but I am not happy with my code. Can you suggest me better kotlin solution?

    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
    }

Model:

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
)

It's learning example, does not have to make any sense.

Upvotes: 0

Views: 87

Answers (1)

IR42
IR42

Reputation: 9672

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()
}

Upvotes: 5

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