How to pattern match multiple types in Scala?

Question

How to perform pattern matching for multiple types in scala ?

I am looking to achieve something like below where pattern match type of a and b and execute the code for the combination of type.

def equals[T](a: T, b: T) = {
    (a,b) match {
        case (a,b) : (String, String) = isEquals(a.asInstanceOf[String],b.asInstanceOf[String])
        case (a,b) : (Int, Int) = isEquals(a.asInstanceOf[Int],b.asInstanceOf[Int])  
    }
}

slouc · Accepted Answer · 2019-03-30 22:32:43Z

3

You were very close:

def equals[T](a: T, b: T) =
  (a, b) match {
    case (a: String, b: String) => println(s"Strings: $a $b")
    case (a: Int, b: Int)       => println(s"Ints: $a $b")
    case _                      => println("Not sure what")
  }

equals("foo", "bar") // Strings: foo bar
equals(12, 34)       // Ints: 12 34
equals(true, false)  // Not sure what

edited Mar 30, 2019 at 22:32

answered Mar 30, 2019 at 22:26

slouc

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3 Comments

Naresh Krishnamoorthy Over a year ago

Thank you so much Slouc.. You saved my time.. I did not find this syntax online.. Can you recommend any website or material where can i look for Scala syntax in general in case of clarification which would save time..

slouc Over a year ago

No problem. Just one thing: when asking a question on SO, it is very useful to provide a MCV example, which makes it both easier for you to reason about your problem, and for other users to answer it. For example, see how I used println instead of your isEquals; that's because isEquals has nothing to do with the problem itself. Regarding resources, when I was starting out I liked this book and this course.

slouc Over a year ago

Also, when you get an answer that helped you solve your problem, established practice is to simply mark the answer as resolved. This way you're saying "yes, this is exactly what I needed", so you don't even have to write "thanks" etc. in the comments. And the person who answered it gets a sense of completion that way, along with some reputation points. That's all. Enjoy your time on SO!

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