Question

我有很多字段的案例类

 case class H(     
                           id: Int, 
                           min: Option[String] = None,
                           max: Option[String] = None,
                           step: Option[String] = None,
                           ...
                           )

如何将一些字段映射到表格？

class TH(tag: Tag) extends Table[H](tag, "H") {
  def id = column[Long]("ID", O.PrimaryKey, O.AutoInc)
  def min = column[Option[String]]("M")

  def * = (id, min) <>(H.tupled, H.unapply)
}

当我尝试这样的时候 - def * = (id, min) <>(H.tupled, H.unapply)，而不是映射所有字段，得到了编译异常。我可以将自定义字段映射到表格吗？

BR！

Answer 1

tupled和unapply只是case类生成的基本函数，它定义了以下函数（以及其他内容）和case类的所有字段。

例如，对于案例类X(a: A, b: B, c: C, d: D)，您有：

def tupled(a: a, b: b, c: c, d: d): X
def unapply(x: X): Option[(A, B, C, D)]

另一方面，使用<>构建的投影需要参数：(f: (U => R), g: (R => Option[U]))，其中U是字段类型的组合。

你并没有依赖于使用＆＃34;自动＆＃34; tupled / unapply如果它们不符合您的需求，您可以提供自己的定义：

class TH(tag: Tag) extends Table[H](tag, "H") {
  def id = column[Long]("ID", O.PrimaryKey, O.AutoInc)
  def min = column[Option[String]]("M")

  def * = (id, min) <> (
    { tuple: (Long, Option[String]) => TH(id, min) },
    { th: TH => Some((th.id, th.min)) }
  )
}

Answer 2

谢谢，试过了。有编译错误。无法使用=> TH编译错误。已更改为H。

Error:Play 2 Compiler:    def * = (id, idUser) <>( {
Error:Play 2 Compiler:                             ^
Error:Play 2 Compiler: 
   }, { hq: TH => Some((hq.id, hq.idUser)) })
                           ^
No matching Shape found.
Error:Play 2 Compiler:  Slick does not know how to map the given types.
Error:Play 2 Compiler: 
 Possible causes: T in Table[T] does not match your * projection. Or you use an unsupported type in a Query (e.g. scala List).
   Required level: slick.lifted.FlatShapeLevel
      Source type: (slick.lifted.Rep[Long], slick.lifted.Rep[Long])
Error:Play 2 Compiler: 
    Unpacked type: (slick.lifted.Rep[Long], slick.lifted.Rep[Long])
      Packed type: Any
   def * = (id, idUser) <>( {
Error:Play 2 Compiler:                         ^
Error:Play 2 Compiler: 
 (compile:compileIncremental) Compilation failed
 Total time: 9 s, completed Sep 3, 2015 11:58:13 AM

Error:(88, -1) Play 2 Compiler: 
 missing parameter type for expanded function
 The argument types of an anonymous function must be fully known. (SLS 8.5)
 Expected type was: ? => ?

案例类：

 case class H(
id: Option[Long] = None,
idUser: Option[Long] = None,
title: Option[String] = None,
...)

光滑的桌子：

class TH(tag: Tag) extends Table[H](tag, "H") {

  def id = column[Long]("ID", O.PrimaryKey, O.AutoInc)

  def idUser = column[Long]("ID_USER")

  foreignKey("USER_FK", idUser, TableQuery[TUser])(_.id, onUpdate = ForeignKeyAction.Restrict, onDelete = ForeignKeyAction.Cascade)

  def * = (id, idUser) <>( {
    case (id: Option[Long], idUser: Option[Long]) => H(id, idUser)
  }, { th: TH => Some((th.id, th.idUser)) })
}

光滑3映射自定义字段

2 个答案: