重载“apply"方法时:错误消息“值元组不是对象的成员" [英] When overloading `apply` method: Slick error message 'value tupled is not a member of object'

问题描述

我需要能够通过在某些情况下提供除 id 之外的所有值来创建 User 对象，以便 User 对象采用注意为自己分配一个自动生成的值.

I need an ability to create a User object by providing all the values except id in certain cases, such that the User object takes care of assigning itself an auto-generated value.

为此，我重载了伴生对象中的 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.

For this I have overloaded the apply method in the companion object, like shown below. But this is causing the compile time error: 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

Solutions mentioned on StackOverflow and other blogs aren't working, such as: 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)

}

推荐答案

问题的根源在于重载了 apply def.

The source of your problem is that overloaded apply def.

tupled 不适用于 case class 的 少于 2 个参数 或 overloaded apply.

tupled does not work with case class's with less than 2 parameters or overloaded apply.

就 slick 的 *(或全部)映射和 <> 而言，它应该是这样的，

As far as slick's * (or all) mapping and <> is concerned, it is supposed to be like,

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

这样，

• func1 将该元组 (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, ...).

• func1 takes that tuple (tupleMember1, tupleMember2, ...) as input and returns an instance of mapped class/case class.
• func1 takes an instance of mapped class/case class and returns that tuple (tupleMember1, tupleMember2, ...).

因此您可以提供任何功能...满足这些要求.

So you can provide any function... which meets these requirements.

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)

}

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