重载“apply”方法时：光滑的错误消息“值元组不是对象的成员”

我需要有能力创造一个User对象通过提供除id在某些情况下，使得User对象负责为自己分配一个自动生成的值。

为此，我重载了伴随对象中的 apply 方法，如下所示。但这会导致编译时错误：value tupled is not a member of object.

StackOverflow 和其他博客上提到的解决方案不起作用，例如：http://queirozf.com/entries/slick-error-message-value-tupled-is-not-a-member-of-object http://queirozf.com/entries/slick-error-message-value-tupled-is-not-a-member-of-object

case class User(id: Long, firstName: String, lastName: String, mobile: Long, email: String)

object User {
  private val seq = new AtomicLong

  def apply(firstName: String, lastName: String, mobile: Long, email: String): User = {
    User(seq.incrementAndGet(), firstName, lastName, mobile, email)
  }
}

class UserTableDef(tag: Tag) extends Table[User](tag, "user") {

  def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
  def firstName = column[String]("first_name")
  def lastName = column[String]("last_name")
  def mobile = column[Long]("mobile")
  def email = column[String]("email")

  override def * =
    (id, firstName, lastName, mobile, email) <> (User.tupled, User.unapply)

}

你的问题的根源是超载apply def.

tupled不适用于case class's with less than 2 parameters or overloaded apply.

就光滑而言*（或全部）映射和<>关心的是，它应该是这样的，

def * = (tupleMember1, tupleMember2, ...) <> (func1, func2)

这样，

• func1接受那个元组(tupleMember1, tupleMember2, ...)作为输入并返回映射类/案例类的实例。
• func1获取映射类/案例类的实例并返回该元组(tupleMember1, tupleMember2, ...).

所以你可以提供任何满足这些要求的功能。

case class User(id: Long, firstName: String, lastName: String, mobile: Long, email: String)

object User {
  private val seq = new AtomicLong

  def apply(firstName: String, lastName: String, mobile: Long, email: String): User = {
    User(seq.incrementAndGet(), firstName, lastName, mobile, email)
  }

  def mapperTo(
    id: Long, firstName: String,
    lastName: String, mobile: Long, email: String
  ) = apply(id, firstName, lastName, mobile, email)

}

class UserTableDef(tag: Tag) extends Table[User](tag, "user") {

  def id = column[Long]("id", O.PrimaryKey, O.AutoInc)
  def firstName = column[String]("first_name")
  def lastName = column[String]("last_name")
  def mobile = column[Long]("mobile")
  def email = column[String]("email")

  override def * =
    (id, firstName, lastName, mobile, email) <> ((User.mapperTo _).tupled, User.unapply)

}