为什么这个 switch 语句不匹配子字符串？

Question

我试图将字符串变量的子字符串与 switch 语句匹配：

#$value = "55"
#$value = "55-"
#$value = "55+"
$value = "+55"

switch ($Value) {
    "^\+" {"Starts With +"}
    "^\d" {"Starts With a digit"}

    "+$" {"Ends with +"}
    "-$" {"Ends with -"}
}

switch 语句不会触发。即使我这样做了"^\+.*" {"Starts With +"}。我确实需要部分匹配$Value. 我究竟做错了什么？

Answer 1

发生这种情况是因为默认情况下switch 不需要正则表达式。要使用正则表达式进行匹配，请传递-regexfor 语句。就像这样，

 $value = "+55"
 switch -regex ($Value) {
     "^\+" {"Starts With +"}
     "^\d" {"Starts With a digit"}     
     "\+$" {"Ends with +"} #Remember to escape quantifier
     "-$" {"Ends with -"}
     default {"no match"}
 }
# Output
Starts With +