从多维数组中安全地获取元素

Question

val arr = Array.fill[String](6, 6)("dark")

安全得到:

 arr(9)(9)
>java.lang.ArrayIndexOutOfBoundsException: 9

我用了类似的东西(但很难看):

arr.lift(2).flatMap(_.lift(2))
>res0: Option[String] = Some(dark)

有更好的方法吗?

Answer 1

如果你想要更易读的内容，你可以使用a来理解:

for {
 inner <- arr.lift(7)
 value <- inner.lift(2)
} yield value

Answer 2

把我的评论变成答案:

val arr = Array.fill[String](6, 6)("dark")
implicit class SafeArrayOps[T](arr: Array[Array[T]]) {
  def safeGet(x: Int, y: Int) = {
    if (x < 0 || x >= arr.length) None
    else {
      val inner = arr(x)
      if (y <= 0 || y >= inner.length) None
      else Some(inner(y))
    }
  }
}
arr.safeGet(2,2)                                //> res0: Option[String] = Some(dark)
arr.safeGet(7,7)                                //> res1: Option[String] = None
arr.safeGet(2,7)                                //> res2: Option[String] = None
arr.safeGet(7,2)                                //> res3: Option[String] = None
arr.safeGet(-1, 2)                              //> res4: Option[String] = None
arr.safeGet(2,-1)                               //> res5: Option[String] = None