Slick 3.1.x CRUD：如何提取插入的行id？ [英] Slick 3.1.x CRUD: how to extract the inserted row id?

问题描述

我有以下耦合到模型的DAO实现，并在数据库中持久化一个新实体(注意能够获取序列生成的id的额外步骤)，并且编译得很好(尚未实际测试)：

// this is generated by the Slick codegen
case class UserRow(id: Long, ...
class User(_tableTag: Tag) extends Table[UserRow](_tableTag, "user")
lazy val User = new TableQuery(tag => new User(tag))

// function to persist a new user
def create(user: UserRow): Future[UserRow] = {
  val insertQuery = User returning User.map(_.id) into ((row, id) => row.copy(id = id))
  val action = insertQuery += user
  db.run(action)
}

现在我尝试使DAO泛型并与模型分离，并拥有(请查看GenericDao.scala中的完整源代码)：

def create(entity: E): Future[E] = {
  val insertQuery = tableQuery returning tableQuery.map(_.id) into ((row, id) => row.copy(id = id))
  val action = insertQuery += entity
  db.run(action)
}

但这会导致编译器错误：

[error] /home/bravegag/code/play-authenticate-usage-scala/app/dao/GenericDao.scala:81: type mismatch;
[error]  found   : GenericDao.this.driver.DriverAction[insertQuery.SingleInsertResult,slick.dbio.NoStream,slick.dbio.Effect.Write]
[error]     (which expands to)  slick.profile.FixedSqlAction[dao.Entity[PK],slick.dbio.NoStream,slick.dbio.Effect.Write]
[error]  required: slick.dbio.DBIOAction[E,slick.dbio.NoStream,Nothing]
[error]       db.run(action)
[error]              ^
[error] one error found
[error] (compile:compileIncremental) Compilation failed

首先，我不确定为什么返回类型与耦合版本不同，以及如何修复/提取具有分配的序列ID的新创建的实体。

推荐答案

将函数的返回类型更改为Future[Entity[PK]]而不是Future[E]

def create(entity: E): Future[Entity[PK]] = {
  val insertQuery = tableQuery returning tableQuery.map(_.id) into ((row, id) => row.copy(id = id))
  val action = insertQuery += entity
  db.run(action)
}

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