Scala 索姆坚持'；id'；未定义

我只是想学习SORM，并在玩我认为是一些简单的示例代码。致：

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")  )

尝试编译此文件时，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]                                                ^

如果我将图书声明更改为：

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]            ^

---

为这个新手问题道歉。毫无疑问，我同时学习Scala是一个促成因素。

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，您仍然可以使用持久化的访问与

图书相同的界面

至于为什么会发生这种情况，这似乎是Scala的一个bug，而且

旁注
在case类声明中不要使用
var
s。不变性是case类的全部要点。正确的声明是：

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

这和

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

谢谢你，尼基塔，这解决了我的问题。我很欣赏案例课上关于var vs val的注释，这绝对是我的疏忽。注意，我从SORM文档中复制了我的原始声明，在存储新实体（）下。