SORM 持久化 'id' 未定义

Posted 2023-04-12

【中文标题】SORM 持久化 \'id\' 未定义

【英文标题】：SORM Persisted 'id' undefinedSORM 持久化 'id' 未定义

【发布时间】：2013-11-16 23:10:09

【问题描述】：

我只是在尝试学习 SORM，并且正在使用我认为是一些简单的示例代码。对白衣：

case class Book(var author:String, var title:String);

object Db extends Instance(
  entities = Set(Entity[Book]()),
  url = "jdbc:h2:mem:test",
  user = "",
  password = "",
  initMode = InitMode.Create
)

然后：

val b : Book with Persisted = Db.save( Book("foo","bar")  )

尝试编译时，我得到：

[error] /Users/rjf/IdeaProjects/PlayTest/app/controllers/Application.scala:22: type mismatch;
[error]  found   : models.Book
[error]  required: sorm.Persisted with models.Book
[error]     val b : Book with Persisted = Db.save( Book("foo","bar")  )
[error]                                                ^

如果我将 Book 声明更改为：

case class Book(var author:String, var title:String) extends Persisted;

然后我得到：

[error] /Users/rjf/IdeaProjects/PlayTest/app/models/Book.scala:17: class Book needs to be abstract, since:
[error] it has 2 unimplemented members.
[error] /** As seen from class Book, the missing signatures are as follows.
[error]  *  For convenience, these are usable as stub implementations.
[error]  */
[error]   def id: Long = ???
[error]   def mixoutPersisted[T]: (Long, T) = ???
[error] case class Book(var author:String, var title:String) extends Persisted;
[error]            ^

为新手问题道歉。毫无疑问，我同时学习 Scala 是一个促成因素。

【参考方案1】：

要解决您的问题，只需删除显式类型注释：

val b = Db.save( Book("foo","bar") )

别担心，您仍然可以访问与Book with Persisted 相同的界面。

至于为什么会这样，这似乎是Scala的一个bug，it's been reported。

附注

不要在case类声明中使用vars。不变性是案例类的重点。正确的声明是：

case class Book(author:String, title:String)

与

相同

case class Book(val author:String, val title:String)

【讨论】：

谢谢 Nikita，解决了我的问题。我很欣赏我的案例课程中关于 var vs val 的注释，这绝对是我的疏忽。请注意，我在存储新实体 (sorm-framework.org/Documentation.html) 下复制了 SORM 文档中的原始声明。