由网友(顾你安稳)分享简介：目前我有这样的东西：val q = for {department <- departments if department.id === xemployee <- employees if employee.departmentId === department.id} yield (department, emp...

目前我有这样的东西：

val q = for {
  department <- departments if department.id === x
  employee <- employees if employee.departmentId === department.id
} yield (department, employee)

这将为我提供：

(sales, john)
(sales, bob)
(finance, william)
(finance, helen)

然后我按部门对结果进行分组：

val grouped = results.groupBy(_._1).mapValues(_.map(_._2))

给我：

(sales -> (john, bob))
(finance -> (wiliam, helen)

我希望避免使用元组。虽然在这个简单的示例中很清楚，但如果我希望部门、经理、副手和员工列表以结构化的格式出现，它很快就会变得无法管理。如果源代码中的查询和结果处理彼此不接近，则情况尤其如此。

如何在查询中生成元组以外的其他内容？

我尝试生成案例类：

case class DeptEmployeeRow(department: Department, employee: Employee)

val q = for {
  department <- departments if department.id === x
  employee <- employee if employee.id
} yield DeptEmployeeRow(department, employee)

但斯利克不喜欢这样。使用单态Case类和Slick的CaseClassShape不起作用，因为它只支持内置类型，即我可以使用：

yield DeptEmployeeRow(department.name, employee.name)

但不是

yield DeptEmployeeRow(department, employee)

推荐答案

元组实际上相当强大，尤其是在模式匹配的上下文中。例如，您可以这样访问元组内容：

case class DeptEmployeeRow(department: Department, employee: Employee)

val q = for {
  department <- departments if department.id === x
  employee <- employees if employee.departmentId === department.id
} yield (department, employee)

使用模式匹配访问元组：

val result1: DeptEmployeeRow = db.run(q.result).map {
  case (department, employee) => DeptEmployeeRow(department, employee)
}

或使用快捷方式：

val result2: DeptEmployeeRow = db.run(q.result).map(_.map(DeptEmployeeRow.tupled))

您可以进一步模拟1：N关系：

case class DeptWithEmployees(department: Department, employees: Seq[Employee])

val result3: DeptWithEmployees = db.run(q.result).map { results =>
  results.groupBy(_._1).map {          // assumption that _._1 is your department id
    case (dept, grp) => DeptWithEmployees(dept, grp.map(_._2))
  }
}