Pattern Matching `@` Symbol

Question

Given this Person case class:

scala> case class Person(name: String, age: Int) {} defined class Person 

... and this instance

scala> val b = Person("Kevin", 100) b: Person = Person(Kevin,100) 

Is there a reason to prefer this code (with @)

scala> b match {      |    case p @ Person(_, age) => println("age")      |    case _ => println("none")      | } age 

... over the following?

scala> b match {      |    case Person(_, age) => println("age")      |    case _ => println("none")      | } age 

Perhaps I'm missing the meaning/power of @?

Answer 1

You only include the @ when you want to also deal with the object itself. Hence:

that match{   case p @ Person(_, age) if p != bill => age   case Person(_, age) => age - 15   case _ => println("Not a person") } 

Otherwise, there's no real point in including it.

Answer 2

Regarding the comments for the above answer.

Consider this case class.

case class Employee(name: String, id: Int, technology: String) 

while doing pattern matching.

case e @ Employee(_, _, "scala") => e.name // matching for employees with only scala technology ... it works  case x: Employee => x.name // It also works  case e: Employee(_, _, "scala") => e.name // matching for employees with only scala technology ... **wont't work**