它使人们能够将匹配的模式绑定到变量.例如，考虑以下内容:

It enables one to bind a matched pattern to a variable. Consider the following, for instance:

val o: Option[Int] = Some(2)

您可以轻松提取内容:

o match {
  case Some(x) => println(x)
  case None =>
}

但是，如果您不希望Some的 content ，而是该选项本身，该怎么办?可以这样实现:

But what if you wanted not the content of Some, but the option itself? That would be accomplished with this:

o match {
  case x @ Some(_) => println(x)
  case None =>
}

请注意，@可以在任何级别使用，而不仅仅是在匹配项的***级别使用.

Note that @ can be used at any level, not just at the top level of the matching.