如何覆盖子类中的macwire注入器

Question

Play web框架允许注入“筛选器”列表来对请求(gzip、cors、日志记录等)执行通用处理。

package play.api

trait BuiltInComponents {
  ...
  lazy val httpFilters: Seq[EssentialFilter] = Nil
  <stuff that uses httpFilters>
  ...
}

我希望有一套共同的这些过滤器(和其他东西)。

package example

import play.api.BuildInComponents

trait MyCommonComponents extends BuiltInComponents {
    ...
    override lazy val filters = Seq(
      wire[Filter1],
      wire[Filter2],
      wire[Filter3]
    )
    ...
}

可由子类使用的

package example.foo

import example.MyCommonComponents

trait MyFooComponents extends MyCommonComponents {
    ...
}

或添加到子类中

package example.bar

import example.MyCommonComponents

trait MyBarComponents extends MyCommonComponents {
    ...
    override lazy val filters = super.filters :+ wire[Filter4]
    ...
}

我试过的东西

1. 上面的密码。不能在懒惰的val中使用super。
2. 将httpFilters改为def。由于BuiltInComponents需要一个稳定的值
3. 添加lazy val httpFilters = filters和def filters: Seq[EssentialFilter] = ...，然后酌情重写filters。Macwire抱怨类型不明确。

我能做些什么来实现可选附加的过滤器列表？

Answer 1

我可能不明白你的情况，但简单的怎么了

import com.softwaremill.macwire._
import play.api.BuiltInComponents
import play.api.mvc.{EssentialAction, EssentialFilter}

class Filter1 extends EssentialFilter {
  override def apply(next: EssentialAction) = next
}

class Filter2 extends EssentialFilter {
  override def apply(next: EssentialAction) = next
}

class Filter3 extends EssentialFilter {
  override def apply(next: EssentialAction) = next
}

trait MyCommonComponents extends BuiltInComponents {

  protected lazy val baseFilters: Seq[EssentialFilter] = Seq(
    wire[Filter1],
    wire[Filter2],
  )

  override def httpFilters = baseFilters
}


trait MyFooComponents extends MyCommonComponents {

  protected lazy val fooFilters = baseFilters :+ wire[Filter3]

  override def httpFilters = fooFilters
}

或者这个

trait MyBarComponents extends MyCommonComponents {

  private lazy val barFilters = Seq[EssentialFilter](wire[Filter3])

  override def httpFilters = super.httpFilters ++ barFilters
}

为什么要重写您的lazy val而不是设计为要重写的基本httpFilters。