我可以在scala中组合多个字符串匹配的情况吗？

Question

可以将以下两种情况合并为一个case子句，因为它们都执行相同的操作？

e match { 
    case "hello" => e + "world" 
    case "hi" => e + "world 
} 

还等什么，如果我想匹配使用startsWith例如，

e match { case e.startsWith("he") | e.startsWith("hi") => ... } 

Answer 1

是的，你可以简单地使用or (|)到match的pattern之一，

scala> "hi" match { case "hello" | "hi" => println("fantastic") case _ => println("very very bad")} 
fantastic 

scala> "hello" match { case "hello" | "hi" => println("fantastic") case _ => println("very very bad")} 
fantastic 

scala> "something else" match { case "hello" | "hi" => println("fantastic") case _ => println("very very bad")} 
very very bad 

你也可以使用正则表达式进行模式匹配，当匹配的标准很多时特别有用，

scala> val startsWithHiOrHello = """hello.*|hi.*""".r 
startsWithHiOrHello: scala.util.matching.Regex = hello.*|hi.* 

scala> "hi there" match { case startsWithHiOrHello() => println("fantastic") case _ => println("very very bad")} 
fantastic 

scala> "hello there" match { case startsWithHiOrHello() => println("fantastic") case _ => println("very very bad")} 
fantastic 

scala> "non of hi or hello there" match { case startsWithHiOrHello() => println("fantastic") case _ => println("very very bad")} 
very very bad 

参考Scala multiple type pattern matching和Scala match case on regex directly