Cart.scala

case class Cart
(id: CartId,
 status: StatusType.Value,
 customerId: CustomerId,
 cartItems: List[CartItem])
 extends Entity[CartId]

Cart2.scala

case class Cart
(id: CartId,
 status: StatusType.Value,
 customerId: CustomerId,
 cartItems: List[CartItem]) extends Entity[CartId] {

  val sizeOfCartItems = cartItems.size

  val quantityOfCartItems = cartItems.foldLeft(0)(_ + _.quantity)

  def containsItemId(itemId: ItemId): Boolean =
    cartItems.exists {
      _.itemId == itemId
    }

  def addCartItem(cartItem: CartItem): Cart = {
    require(cartItem.quantity > 0)
    cartItems.find(_.itemId == cartItem.itemId).map {
      currentItem =>
        val newCartItem = currentItem.
          addQuantity(cartItem.quantity).ensuring(_.quantity > 0)
        copy(cartItems = newCartItem :: 
          cartItems.filterNot(_.itemId == cartItem.itemId))
    }.getOrElse {
      copy(cartItems = cartItem :: cartItems)
    }
  }

  def addCartItem
  (cartItemId: CartItemId,
  item: Item,
  quantity: Int,
  isInStock: Boolean): Cart =
    addCartItem(CartItem(
      cartItemId, StatusType.Enabled,
      cartItems.size + 1, item.id,
      quantity, isInStock))

  def removeCartItemByItemId(itemId: ItemId): Cart =
    cartItems.find(_.itemId == itemId).map {
      e =>
        copy(cartItems = cartItems.filterNot(_.itemId == itemId))
    }.getOrElse(this)

  def incrementQuantityByItemId(itemId: ItemId): Cart =
    cartItems.find(_.itemId == itemId).map {
      cartItem =>
        val newCartItem = cartItem.incrementQuantity.
          ensuring(_.quantity > 0)
        copy(cartItems = newCartItem ::
          cartItems.filterNot(_.itemId == itemId))
    }.getOrElse(this)

  def updateQuantityByItemId(itemId: ItemId, quantity: Int): Cart = {
    require(quantity > 0)
    cartItems.find(_.itemId == itemId).map {
      cartItem =>
        val newCartItem = cartItem.withQuantity(quantity).
          ensuring(_.quantity > 0)
        copy(cartItems = newCartItem ::
          cartItems.filterNot(_.itemId == itemId))
    }.getOrElse(this)
  }

}

CartItem.scala

case class CartItem
(id: CartItemId,
status: StatusType.Value,
no: Int,
itemId: ItemId,
quantity: Int,
inStock: Boolean)

CartItem2.scala

case class CartItem
(id: CartItemId,
status: StatusType.Value,
no: Int,
itemId: ItemId,
quantity: Int,
inStock: Boolean) {

  def incrementQuantity: CartItem = addQuantity(1)

  def addQuantity(otherQuantity: Int): CartItem = 
    copy(quantity = quantity + otherQuantity)

  def withQuantity(quantity: Int): CartItem =
    copy(quantity = quantity)

}

Contact.scala

case class Contact(email: String, phone: String)

Customer.scala

case class Customer
(id: CustomerId,
 status: StatusType.Value,
 name: String,
 sexType: SexType.Value,
 zipCode: ZipCode,
 pref: Pref.Value,
 cityName: String,
 addressName: String,
 buildingName: Option[String] = None,
 loginName: String,
 password: String)
  extends Entity[CustomerId]

Customer2.scala

case class Customer
(id: CustomerId,
 status: StatusType.Value,
 name: String,
 sexType: SexType.Value,
 profile: CustomerProfile,
 config: CustomerConfig)
  extends Entity[CustomerId]

CustomerConfig.scala

case class CustomerConfig
(loginName: String,
 password: String)

CustomerProfile.scala

case class CustomerProfile
(postalAddress: PostalAddress,
 contact: Contact)

Entity.scala

trait Entity[ID <: Identifier[_]] {

  val id: ID

  override def equals(obj: Any): Boolean = this match {
    case that: Entity[_] => id == that.id
    case _ => false
  }

  override def hashCode: Int = 31 * id.##

}

Item.scala

case class Item
(id: ItemId,
 status: StatusType.Value,
 name: String,
 description: Option[String] = None,
 price: BigDecimal)
  extends Entity[ItemId]

PostalAddress.scala

case class PostalAddress
(zipCode: ZipCode,
 pref: Pref.Value,
 cityName: String,
 addressName: String,
 buildingName: Option[String] = None)

Pref.scala

object Pref extends Enumeration {

   val 北海道,青森県,岩手県,宮城県,秋田県,山形県,福島県,
   茨城県,栃木県,群馬県,埼玉県,千葉県,東京都,神奈川県,
   新潟県,富山県,石川県,福井県,山梨県,長野県,岐阜県,
   静岡県,愛知県,三重県,滋賀県,京都府,大阪府,兵庫県,
   奈良県,和歌山県,鳥取県,島根県,岡山県,広島県,山口県,
   徳島県,香川県,愛媛県,高知県,福岡県,佐賀県,長崎県,
   熊本県,大分県,宮崎県,鹿児島県,沖縄県 = Value

 }

ZipCode.scala

case class ZipCode(areaCode: String, cityCode: String) {
  def asString = s"$areaCode-$cityCode"
}