大小写 类 问题的隐式转换

Question

我正在尝试将一种情况 class 隐式转换为另一种情况 class，但无法使代码正常工作。我的编辑器给我的错误是 Seq[LegacyPhase] 没有转换为预期的 Seq[Phase]。谁能指出我的方向？提前致谢！

implicit def legacyToDashboardBrand(brand: LegacyDashboardBrand)(implicit session: Session): DashboardBrand = {
  val phaseSeq: Seq[Phase] = (for { phaseDataset <- dashboardPhasesQ if phaseDataset.brandId === brand.id
  } yield phaseDataset).list.toSeq
  DashboardBrand(id = brand.id, projectId = brand.projectId, name = brand.name, currentPhase = brand.currentPhase, phases = phaseSeq)
}

implicit def legacyToDashboardPhase(phase: LegacyPhase): Phase = {
  Phase(id = phase.id, brandId = phase.brandId, title = phase.title, steps = Seq())
}

编辑：如果我在第一个隐式转换定义中执行第二个隐式转换行，它就可以工作。

implicit def legacyToDashboardBrand(brand: LegacyDashboardBrand)(implicit session: Session): DashboardBrand = {
  val legacyPhaseSeq = (for { 
    phaseDataset <- dashboardPhasesQ if phaseDataset.brandId === brand.id
  } yield phaseDataset).list.toSeq
  val phaseSeq: Seq[Phase] = legacyPhaseSeq.map(phase => 
    Phase(id = phase.id, brandId = phase.brandId, title = phase.title, steps = Seq())
  )

  DashboardBrand(id = brand.id, projectId = brand.projectId, name = brand.name, currentPhase = brand.currentPhase, phases = phaseSeq)
}

Answer 1

您的第二个解决方案（使用重复代码）有效，因为您明确地将 Seq[LegacyPhase] 转换为 Seq[Phase]。

您可以通过在第一个 legacyToDashboardBrand 函数中为 LegacyPhase => Phase 转换函数添加隐式参数来获得相同的结果：

implicit def legacyToDashboardBrand(
  brand: LegacyDashboardBrand
)(implicit 
  session: Session,
  phaseConv: LegacyPhase => Phase
): DashboardBrand = {
  val phaseSeq: Seq[Phase] = (for { 
    phaseDataset <- dashboardPhasesQ if phaseDataset.brandId === brand.id
  } yield phaseDataset).list.map(phaseConv).toSeq
  DashboardBrand(
    id = brand.id, projectId = brand.projectId, name = brand.name,
    currentPhase = brand.currentPhase, phases = phaseSeq
  )
}

这样你的 LegacyDashboardBrand => DashboardBrand 转换函数，使用你的 LegacyPhase => Phase 转换函数。

注意：我不认为在隐式转换函数中查询数据库是个好主意。隐式转换本身相当 "magical" 并使您的代码更难理解，添加查询数据库等副作用只会使它更神奇。