在Scala中，我如何建议自己的方法? [英] In Scala how can I advise my own methods?

问题描述

我想这样做:

trait Renderable {
    def render: String
}

trait Parens extends Renderable {
    abstract override def render = "(" + super.render + ")"
}

object Foo extends Renderable with Parens {
    def render = "Hello"
}

但是这不起作用，因为线性化顺序将Parens放在Foo之后 (当然，Foo总是来的)所以Parens不能建议Foo.render.

But this does not work because the linearization order puts Parens after Foo (Foo always comes, of course) so Parens can't advise Foo.render.

我最终这样做:

trait FooRender {
    def render = "Hello"
}

object Foo extends FooRender with Parens {
}

但是有时候我真的不想这么做，因为它会使事情分崩离析.作为 据我所知，线性化顺序是唯一的障碍， 但我不知道改变这种状况的方法.什么可以使这种清洁剂?

But sometimes I really don't want to do that because it breaks things up. As far as I can tell, linearization order is the only thing getting in the way, but I don't know a way to change that. What might make this cleaner?

推荐答案

如何将表示逻辑(render)和实际内容(value)分开?

How about separating the presentation logic (render) and the actual contents (value)?

trait Renderable {
  def value : String
  def render = value // default presentation logic, simple rendering.
}

trait Parens extends Renderable {
  override def render :String = "(" + value + ")" // parens rendering.
}

object Foo extends Parens {
  def value = "Hello"
}

println(Foo.render) // prints '(Hello)'

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编辑

找到了一种可以完成几乎所有想要的事情的方法，请检查一下:

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Edit

Found a way you can do pretty much what you wanted, check it out:

trait Renderable {
  def render: String
}

trait Parens extends Renderable {
  abstract override def render = "(" + super.render + ")"
}

class Foo extends Renderable {
  def render = "Hello"
}

val foo = new Foo with Parens
println(foo.render)

您不能使用object，因为您需要在创建时实现特征，但是如果您可以控制实例的创建，那么这可能会起作用:).

You can't use an object since you need to implement the trait at creation time, but if you can control the instance creation then this might work :).

我很确定否则是不可能的(如果我错了，请有人纠正我)

I'm pretty sure it's not possible to do it otherwise (someone please correct me if I'm wrong)

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