Scala Pattern Matching
It is a generalization of C or Java’s switch statement. This matching method is used instead of a switch statement. It is defined in Scala’s root class Any and therefore is available for all objects. The match method takes a number of cases as an argument. Each alternative takes a pattern and one or more expressions that will be performed if the pattern matches. A symbol => is used to separate the pattern from the expressions.
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e.g.
object Intellipaat {
def main(args: Array[String]) {
println(matchValue(2))
}
def matchValue(i: Int): String = i match {
case 1 => "one"
case 2 => "two"
case 3=> "three"
case _=> "unknown"
}
}
Output
two
If patterns are of a different type in different cases use Any except Int and String in the above example.
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Case Classes in Scala
These are the special types of classes that are used for pattern matching with case expressions. By adding a case keyword there is the number of advantages which are:
- The compiler automatically changes the constructor arguments into immutable fields.
- The compiler automatically includes equals, hashCode and toString methods to the class
Syntax
case class Calculator(Value: Type)
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e.g.
object Intellipaat {
def main(args: Array[String]) {
val a = new employee(1, “abc”)
val b = new employee(2, “xyz”)
val c = new employee(3, “pgr”)
for (employee <- List(a, b, c)) {
employee match {
case employee(1, “abc”) => println("Hello abc")
case employee(2, “xyz”) => println(“Hello xyz”)
case employee(id, employee_name) => println("ID: " +id + ", Employee:" + employee_name)
}
}
}
case class employee(id: Int, employee_name: String) // case class
}
Output
Hello abc
Hello xyz
ID: 3, Employee: pqr
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