"Kotlin Koans - Collections"의 두 판 사이의 차이

59번째 줄: 59번째 줄:
{{참고|#TestShop.kt & Shop.kt}}
{{참고|#TestShop.kt & Shop.kt}}
<source lang='kotlin'>
<source lang='kotlin'>
// Return customers who have more undelivered orders than delivered
fun Shop.getCustomersWithMoreUndeliveredOrdersThanDelivered(): Set<Customer> = customers.filter {
    val (delivered, undelivered) = it.orders.partition { it.isDelivered }
    undelivered.size > delivered.size
}.toSet()
</source>
</source>


64번째 줄: 69번째 줄:
{{참고|#TestShop.kt & Shop.kt}}
{{참고|#TestShop.kt & Shop.kt}}
<source lang='kotlin'>
<source lang='kotlin'>
 
// Return the set of products that were ordered by every customer
fun Shop.getSetOfProductsOrderedByEveryCustomer(): Set<Product> {
    val allProducts = customers.flatMap { it.orders.flatMap { it.products }}.toSet()
    return customers.fold(allProducts, {
        orderedByAll, customer ->
        orderedByAll.intersect(customer.orders.flatMap { it.products }.toSet())
    })
}
</source>
</source>



2019년 4월 7일 (일) 01:01 판

# Kotlin Koans
Kotlin Koans - Introduction
Kotlin Koans - Conventions
Kotlin Koans - Collections
Kotlin Koans - Properties
Kotlin Koans - Builders
Kotlin Koans - Generics

1 Introduction

Kotlin

2 Filter map

Kotlin

3 All Any and other predicates

Kotlin

4 FlatMap

Kotlin

5 Max min

Kotlin

6 Sort

Kotlin

7 Sum

Kotlin

8 GroupBy

Kotlin

9 Partition

Kotlin
Copy
// Return customers who have more undelivered orders than delivered
fun Shop.getCustomersWithMoreUndeliveredOrdersThanDelivered(): Set<Customer> = customers.filter {
    val (delivered, undelivered) = it.orders.partition { it.isDelivered }
    undelivered.size > delivered.size
}.toSet()

10 Fold

Kotlin
Copy
// Return the set of products that were ordered by every customer
fun Shop.getSetOfProductsOrderedByEveryCustomer(): Set<Product> {
    val allProducts = customers.flatMap { it.orders.flatMap { it.products }}.toSet()
    return customers.fold(allProducts, {
        orderedByAll, customer ->
        orderedByAll.intersect(customer.orders.flatMap { it.products }.toSet())
    })
}

11 Compound tasks

Kotlin
Copy
// Return the most expensive product among all delivered products
// (use the Order.isDelivered flag)
fun Customer.getMostExpensiveDeliveredProduct(): Product? {
    return orders.filter { it.isDelivered }.flatMap { it.products }.maxBy { it.price }
}

// Return how many times the given product was ordered.
// Note: a customer may order the same product for several times.
fun Shop.getNumberOfTimesProductWasOrdered(product: Product): Int {
    return customers.flatMap { it.getOrderedProductsList() }.count { it == product }
}

fun Customer.getOrderedProductsList(): List<Product> {
    return orders.flatMap { it.products }
}

12 Get used to new style

Kotlin
Copy
fun doSomethingStrangeWithCollection(collection: Collection<String>): Collection<String>? {

    val groupsByLength = collection. groupBy { s -> s.length }

    val maximumSizeOfGroup = groupsByLength.values.map { group -> group.size }.max()

    return groupsByLength.values.firstOrNull { group -> group.size == maximumSizeOfGroup }
}

13 TestShop.kt & Shop.kt

TestShop.kt
Kotlin
Copy
//products
val idea = Product("IntelliJ IDEA Ultimate", 199.0)
val reSharper = Product("ReSharper", 149.0)
val dotTrace = Product("DotTrace", 159.0)
val dotMemory = Product("DotTrace", 129.0)
val dotCover = Product("DotCover", 99.0)
val appCode = Product("AppCode", 99.0)
val phpStorm = Product("PhpStorm", 99.0)
val pyCharm = Product("PyCharm", 99.0)
val rubyMine = Product("RubyMine", 99.0)
val webStorm = Product("WebStorm", 49.0)
val teamCity = Product("TeamCity", 299.0)
val youTrack = Product("YouTrack", 500.0)

//customers
val lucas = "Lucas"
val cooper = "Cooper"
val nathan = "Nathan"
val reka = "Reka"
val bajram = "Bajram"
val asuka = "Asuka"
val riku = "Riku"

//cities
val Canberra = City("Canberra")
val Vancouver = City("Vancouver")
val Budapest = City("Budapest")
val Ankara = City("Ankara")
val Tokyo = City("Tokyo")

fun customer(name: String, city: City, vararg orders: Order) = Customer(name, city, orders.toList())
fun order(vararg products: Product, isDelivered: Boolean = true) = Order(products.toList(), isDelivered)
fun shop(name: String, vararg customers: Customer) = Shop(name, customers.toList())

val shop = shop("jb test shop",
        customer(lucas, Canberra,
                order(reSharper),
                order(reSharper, dotMemory, dotTrace)
        ),
        customer(cooper, Canberra),
        customer(nathan, Vancouver,
                order(rubyMine, webStorm)
        ),
        customer(reka, Budapest,
                order(idea, isDelivered = false),
                order(idea, isDelivered = false),
                order(idea)
        ),
        customer(bajram, Ankara,
                order(reSharper)
        ),
        customer(asuka, Tokyo,
                order(idea)
        ),
        customer(riku, Tokyo,
                order(phpStorm, phpStorm),
                order(phpStorm)
        )

)

val customers: Map<String, Customer> = shop.customers.fold(hashMapOf<String, Customer>(), {
        map, customer ->
        map[customer.name] = customer
        map
})

val orderedProducts = setOf(idea, reSharper, dotTrace, dotMemory, rubyMine, webStorm, phpStorm)

val sortedCustomers = listOf(cooper, nathan, bajram, asuka, lucas, riku, reka).map { customers[it] }

val groupedByCities = mapOf(
        Canberra to listOf(lucas, cooper),
        Vancouver to listOf(nathan),
        Budapest to listOf(reka),
        Ankara to listOf(bajram),
        Tokyo to listOf(asuka, riku)
).mapValues { it.value.map { name -> customers[name] } }
Shop.kt
Kotlin
Copy
data class Shop(val name: String, val customers: List<Customer>)

data class Customer(val name: String, val city: City, val orders: List<Order>) {
    override fun toString() = "$name from ${city.name}"
}

data class Order(val products: List<Product>, val isDelivered: Boolean)

data class Product(val name: String, val price: Double) {
    override fun toString() = "'$name' for $price"
}

data class City(val name: String) {
    override fun toString() = name
}