将 Scala Future[Seq[X]] 与 Seq[Future[Y]] 结合起来，生成 Future[（X，Seq[Y]）]

Question

我在我的实体类中具有以下关系，客户 -

type CustomerWithInvoices = (Custimer,Seq[Invoice])

  def findCustomerWitnInvoices:Future[Seq[CustomerWithInvoices]] = {
    for{
      customers <- findCustomers
      eventualInvoices: Seq[Future[Seq[Invoice]]] = customers.map(customer => findInvoicesByCustomer(customer))

    } yield ???
  }

使用现有的存储库方法如下

def findCustomers:Future[Seq[Customers]] = {...}

def findInvoicesByCustomer(customer:Customer):Future[Seq[Invoice]] = {...}

我试图使用如上所述的表达方式，但我无法找到正确的方法来做到这一点，因为我对Scala相当陌生，非常感谢任何帮助。




Answer 1

我会使用Future.sequence，简化的方法签名是ser sequence采取M[Future[A]]并返回Future[M[A]]这就是我们需要解决你的问题，这是我会写的代码：

val eventualCustomersWithInvoices: Future[Seq[(Customer, Seq[Invoice])]] = for {
      customers <- findCustomers()
      eventualInvoices <- Future.sequence(customers.map(customer => findInvoicesByCustomer(customer)))

    } yield eventualInvoices

请注意，eventualInVoice的类型是Future[Seq[（客户，Seq[发票]）]]]因此Future[Seq[Customer withInVoice]]