Scala 为Slick 3.1.1创建通用更新功能
我有这个功能:Scala 为Slick 3.1.1创建通用更新功能,scala,slick,Scala,Slick,我有这个功能: def updateInvoiceAdminStatusField(id: Int, newAdminStatus: AdminStatus): Future[Int] = { db.run { val adminStatus: Query[Rep[AdminStatus], AdminStatus, Seq] = InvoicesTable.filter(invoice => invoice.id === id).map(invoice =&g
def updateInvoiceAdminStatusField(id: Int, newAdminStatus: AdminStatus): Future[Int] = {
db.run {
val adminStatus: Query[Rep[AdminStatus], AdminStatus, Seq] = InvoicesTable.filter(invoice => invoice.id === id).map(invoice => invoice.status)
adminStatus.update(newAdminStatus)
}
}
我想让它变得通用:
def updateInvoiceField[T](id: Int, fieldExtractor: (Invoices) => Rep[T], newValue: T): Future[Int] = {
db.run {
val adminStatus = InvoicesTable.filter(invoice => invoice.id === id).map(invoice => {
fieldExtractor(invoice)
})
adminStatus.update(newValue)
}
}
但这并不适用于编译。有人能帮忙吗?差不多了。通过以下小改动,它应该可以工作:
// I added below T: ColumnType
def updateInvoiceField[T: ColumnType](id: Int, fieldExtractor: (Invoices) => Rep[T], newValue: T): Future[Int] = {
db.run {
val adminStatus = InvoicesTable.filter(invoice => invoice.id === id).map(invoice => {
fieldExtractor(invoice)
})
adminStatus.update(newValue)
}
}
注意,我添加了这个:ColumnType
,这基本上意味着您需要在作用域中有适当的隐式-特别是转换T
=>ColumnType[T]
。这仅仅是因为,否则T
可能是任何东西,Slick
将无法找到如何转换它
因此,对于String
、Int
等内容,显然您已经有了适当的对话(从profile/driver中的api
导入)。对于自定义类型,您需要使用MappedColumnType
来提供正确的转换。下面的示例(类型安全ID):
implicit def columnType[T]: BaseColumnType[Id[T]] =
MappedColumnType.base[Id[T], Long](toLong, fromLong)
private def fromLong[T](dbId: Long): Id[T] = Id(dbId)
private def toLong[T](id: Id[T]): Long = id.value