scala - Lift:如何使这些关系多态？

Question

我有一个条目
它应该与三个“列表”之一有关，称它们为 ListA ListB ListC
我无法弄清楚如何使用 LongMappedMapper 做到这一点。
那我怎么能这样做呢？

我想让 List 有多个条目，而不必为每种列表指定 listX 关系。
所以不是 :

class Entry ...{
    object listA extends LongMappedMapper(this,ListA)
    object listB extends LongMappedMapper(this,ListB)
    ...
}

我想要这样的东西:

class Entry ...{
    object list extends PolyLongMappedMapper(this,ListA,ListB,ListC)
    //PolyLongMappedMapper i the example mapper what i want
    ...
}

或者:

class Entry ...{
    object list extends PolyLongMappedMapper(this,BaseListTrait)
    //where BaseListTrait is a Trait shared by all List classes
    //PolyLongMappedMapper i the example mapper what i want
    ...
}

Lift 框架中有什么东西是我想要的吗？什么可与 PolyLongMappedMapper 相媲美？
或者有没有优雅的方法来解决这个问题？

Answer 1

您可以通过以下方式执行此操作:

class A extends LongKeyedMapper[A] with IdPK {
    object entry extends LongMappedMapper(this, Entry)
    ...

class B extends LongKeyedMapper[B] with IdPK {
    object entry extends LongMappedMapper(this, Entry)
    ...

class C extends LongKeyedMapper[C] with IdPK {
    object entry extends LongMappedMapper(this, Entry)
    ...

class Entry extends LongKeyedMapper[Entry] with IdPK {
    def aList = A.findAll(By(A.entry, this))
    def bList = B.findAll(By(B.entry, this))
    def cList = C.findAll(By(C.entry, this))
    ...

你的 list 是:

e.aList, e.bList, e.cList

什么时候:

val e: Entry

埃塔姆。