案例类问题的隐式转换

Question

我正在尝试将一个案例类隐式转换为另一个案例类，但无法使代码正常工作。我的编辑告诉我 Seq[LegacyPhase] 没有转换为预期的 Seq[Phase] 的错误。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，它会起作用。

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（使用重复的代码）有效，因为您将Seq[LegacyPhase] 显式转换为Seq[Phase]。

您可以通过在您的第一个legacyToDashboardBrand 函数中为您的LegacyPhase => Phase 转换函数添加一个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：我认为在隐式转换函数中查询数据库不是一个好主意。隐式转换本身就非常“神奇”，会让你的代码更难理解，添加查询数据库等副作用只会让它变得更神奇。