日期字符串在Scala中不匹配

Question

I used this to define a function that returns 0 if a string matches a pattern, 0 otherwise:

def verif (s:String): Int = {
 val p = """[0-9]{4}-(0[1-9]|1[0-2])-(0[1-9]|[1-2][0-9]|3[0-1]) (2[0-3]|[01][0-9]):[0-5][0-9]:[0-5][0-9].[0-9]{9}""".r
 s match {
 case p(item) => 0  
 case _ => 1
 }
}

When I execute:

verif("2019-07-01 00:00:00.000000000") // Returns 1

I verified my regex on multiple online testors ( here or here ) and it is working.

Answer 1

You defined 3 capturing groups, hence you must pattern match three groups. However, it makes sense to just use non-capturing groups and the code like:

def verif (s:String): Int = {
  val p = """[0-9]{4}-(?:0[1-9]|1[0-2])-(?:0[1-9]|[1-2][0-9]|3[0-1]) (?:2[0-3]|[01][0-9]):[0-5][0-9]:[0-5][0-9]\.[0-9]{9}""".r
  s match {
    case p() => 0  
    case _ => 1
  }
}
println(verif("2019-07-01 00:00:00.000000000"))   // => 0

See the Scala demo

Note you also need to escape the dot to match a literal dot.