如何改善这个功能？ [英] How to improve this function?

问题描述

假设我有一个这样的数据结构：

Suppose I've got a data structure like that:

case class B(bx: Int)
case class A(ax: Int, bs: Seq[B])

我正在编写一个函数 A => Seq [（Int，Option [Int]）] 如下：

I am writing a function A => Seq[(Int, Option[Int])] as follows:

def foo(a: A): Seq[(Int, Option[Int])] = 
  if (a.bs.isEmpty) Seq((a.ax, None)) else a.bs.map(b => (a.ax, Some(b.bx)))

这似乎可行，但我不喜欢分枝。您将如何改善 foo ？

It seems working but I don't like the branching. How would you improve foo ?

推荐答案

另一种方法-添加辅助函数使用 Seq [T] 并返回 Seq [Option [T]] 的函数，其中输出为从不为空-如果输入为空，则输出结果中将只有一个 None 元素：

Another option - add an auxiliary function that takes a Seq[T] and returns a Seq[Option[T]] where the output is never empty - if the input is empty, the output would have a single None element in its result:

def foo(a: A): Seq[(Int, Option[Int])] = toOptions(a.bs.map(_.bx)).map((a.ax, _))

// always returns a non-empty list - with None as the only value for empty input
def toOptions[T](s: Seq[T]): Seq[Option[T]] = s.headOption +: s.drop(1).map(Some(_))

优点：

• 此真正没有分支（包括 getOrElse 这是一种分支，尽管它更优雅）


• 不重复构建元组（ a.ax 叫过一次）


• 关注点分离得很好（构建一个永不空的列表与处理wi A和Bs）

• This truly has no branching (including getOrElse which is a kind of branching, albeit a more elegant one)
• No repetition of building the tuple (a.ax called once)
• Nice separation of concerns (building a never-empty list vs. dealing with A and Bs)

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