我有以下设计问题:
/**
* Those 2 traits are the public API
*/
trait Box {
def include(t: Token): Box
}
trait Token
/**
* Implementation classes
*/
case class BoxImpl(id: Int) extends Box {
/**
* the implementation of this method depends on the implementation
* of the Token trait
* TODO: REMOVE asInstanceOf
*/
def include(t: Token) = BoxImpl(t.asInstanceOf[TokenImpl].id + id)
}
case class TokenImpl(id: Int) extends Token
// use case
val b: Box = new BoxImpl(3)
val o: Token = new TokenImpl(4)
// == BoxImpl(7)
b.include(o)
在上面的代码中,我不想在公共(public)API中公开id
(甚至不将其设置为private[myproject]
,因为这仍然会包含循环我的项目中的依赖项)。
如何才能保持公共(public) API 完整,同时让实现类彼此具有一定的可见性(没有丑陋的强制转换)?
最佳答案
输入参数或成员:
trait Box {
type T <: Token
def include(t: T): Box
//def include(t: Token): Box
}
trait Token
case class BoxImpl(id: Int) extends Box {
type T = TokenImpl
def include(t: T) = BoxImpl(t.id + id)
/*
def include(t: Token) = t match {
case ti: TokenImpl => BoxImpl(ti.id + id)
case _ => throw new UnsupportedOperationException
}
*/
//def include(t: Token) = BoxImpl(t.asInstanceOf[TokenImpl].id + id)
}
case class TokenImpl(id: Int) extends Token
有很多方法可以将其切片和切 block ,因此蛋糕图案,众所周知的小菜一碟:
trait Boxer {
type Token <: Tokenable
trait Box {
def include(t: Token): Box
}
trait Tokenable
}
trait Boxed extends Boxer {
type Token = TokenImpl
case class BoxImpl(id: Int) extends Box {
override def include(t: Token) = BoxImpl(t.id + id)
}
case class TokenImpl(id: Int) extends Tokenable
}
trait User { this: Boxer =>
def use(b: Box, t: Token): Box = b.include(t)
}
object Test extends App with Boxed with User {
val b: Box = new BoxImpl(3)
val o: Token = new TokenImpl(4)
println(use(b, o))
}
关于scala - 具有依赖特征和依赖实现的设计问题,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/13079359/