postgresql - Slick 2.0 通用 CRUD 操作

Question

我一直在寻找如何为公共(public) CRUD 和其他类型的操作实现通用特征，我查看了 this和 this并且指定的方法运行良好。

我想要的是一个通用的插入方法，我的类目前看起来像这样(非通用实现):

object CampaignModel {
  val campaigns = TableQuery[Campaign]

  def insert(campaign: CampaignRow)(implicit s: Session) = {
    campaigns.insert(campaign)
  }
}

到目前为止，我在第一个链接之后尝试的是这个(通用实现):

trait PostgresGeneric[T <: Table[A], A]  {
  val tableReference = TableQuery[T]

  def insertGeneric(row: ? What type goes here ?)(implicit s: Session) = tableReference.insert(row)

}

当我检查 insert 方法时，它看起来正确的类型应该是 T#TableElementType 但我的知识很基础，我无法理解类型，我尝试了 T 和 A 并且编译器说类类型不符合 trait one 的。

其他信息，表格是用 slick 表格生成工具生成的

case class CampaignRow(id: Long, name: Option[String])

/** Table description of table campaign. Objects of this class serve as prototypes for rows in queries. */
class Campaign(tag: Tag) extends Table[CampaignRow](tag, "campaign") {
  def * = (id, name) <>(CampaignRow.tupled, CampaignRow.unapply)

  /** Maps whole row to an option. Useful for outer joins. */
  def ? = (id.?, name).shaped.<>({
    r => import r._; _1.map(_ => CampaignRow.tupled((_1.get, _2)))
  }, (_: Any) => throw new Exception("Inserting into ? projection not supported."))

  /** Database column id AutoInc, PrimaryKey */
  val id: Column[Long] = column[Long]("id", O.AutoInc, O.PrimaryKey)
  /** Database column name  */
  val name: Column[Option[String]] = column[Option[String]]("name")
}

Answer 1

我设法让它发挥作用，这是我的一般特征:

import scala.slick.driver.PostgresDriver
import scala.slick.driver.PostgresDriver.simple._
import path.to.RichTable

trait PostgresGeneric[T <: RichTable[A], A] {

  val tableReference: TableQuery[T]

  def insert(row: T#TableElementType)(implicit s: Session) = 
    tableReference.insert(row)

  def insertAndGetId(row: T#TableElementType)(implicit s: Session) = 
    (tableReference returning tableReference.map(_.id)) += row

  def deleteById(id: Long)(implicit s: Session): Boolean = 
    tableReference.filter(_.id === id).delete == 1

  def updateById(id: Long, row: T#TableElementType)(implicit s: Session): Boolean = 
    tableReference.filter(_.id === id).update(row) == 1

  def selectById(id: Long)(implicit s: Session): Option[T#TableElementType] = 
    tableReference.filter(_.id === id).firstOption

  def existsById(id: Long)(implicit s: Session): Boolean = {
    (for {
      row <- tableReference
      if row.id === id
    } yield row).firstOption.isDefined
  }
}

其中 RichTable 是一个带有 id 字段的抽象类，带有上限约束的这个对于获取 T#TableElementType 的 id 字段很有用(参见 this更多信息):

import scala.slick.driver.PostgresDriver.simple._
import scala.slick.jdbc.{GetResult => GR}

abstract class RichTable[T](tag: Tag, name: String) extends Table[T](tag, name) {
  val id: Column[Long] = column[Long]("id", O.PrimaryKey, O.AutoInc)
}

我的事件表现在看起来像这样:

import scala.slick.driver.PostgresDriver.simple._
import scala.slick.jdbc.{GetResult => GR}
import scala.slick.lifted.TableQuery

case class CampaignRow(id: Long, name: Option[String])

class Campaign(tag: Tag) extends RichTable[CampaignRow](tag, "campaign") {
  def * = (id, name) <>(CampaignRow.tupled, CampaignRow.unapply)

  def ? = (id.?, name).shaped.<>({
    r => import r._; _1.map(_ => CampaignRow.tupled((_1.get, _2)))
  }, (_: Any) => throw new Exception("Inserting into ? projection not supported."))

  override val id: Column[Long] = column[Long]("id", O.AutoInc, O.PrimaryKey)
  val name: Column[Option[String]] = column[Option[String]]("name")
}

实现通用特征的模型如下所示:

 object CampaignModel extends PostgresGeneric[Campaign, CampaignRow] {

   override val tableReference: PostgresDriver.simple.TableQuery[Tables.Campaign] = 
     TableQuery[Campaign]

   def insertCampaign(row: CampaignRow) = {
     insert(CampaignRow(0, "test"))
   }
 }