Scala - case match partial string

问题:

I have the following:

serv match {

    case "chat" => Chat_Server ! Relay_Message(serv)
    case _ => null

}

The problem is that sometimes I also pass an additional param on the end of the serv string, so:

var serv = "chat.message"

Is there a way I can match a part of the string so it still gets sent to Chat_Server?

Thanks for any help, much appreciated :)

回答1:

Use regexes ;)

val Pattern = "(chat.*)".r

serv match {
     case Pattern(chat) => "It's a chat"
     case _ => "Something else"
}

And with regexes you can even easily split parameter and base string:

val Pattern = "(chat)(.*)".r

serv match {
     case Pattern(chat,param) => "It's a %s with a %s".format(chat,param)
     case _ => "Something else"
}

回答2:

Have the pattern matching bind to a variable and use a guard to ensure the variable begins with "chat"

// msg is bound with the variable serv
serv match {
  case msg if msg.startsWith("chat") => Chat_Server ! Relay_Message(msg)
  case _ => null
}

回答3:

In case you want to dismiss any groupings when using regexes, make sure you use a sequence wildcard like _* (as per Scala's documentation).

From the example above:

val Pattern = "(chat.*)".r

serv match {
     case Pattern(_*) => "It's a chat"
     case _ => "Something else"
}