Classes

Classes in Scala are static templates that can be instantiated into many objects at runtime. Here is a class definition which defines a class Point:

class Point(x: Int, y: Int) {
  override def toString(): String = "(" + x + ", " + y + ")"
}

The class defines two variables x and y and one method toString.

Classes in Scala are parameterized with constructor arguments. The code above defines two constructor arguments, x and y; they are both visible in the whole body of the class. In our example they are used to implement toString.

Classes are instantiated with the new primitive, as the following example will show:

object Classes {
  def main(args: Array[String]) {
    val pt = new Point(1, 2)
    println(pt)
  }
}

The program defines an executable application Classes in the form of a top-level singleton object with a main method. The main method creates a new Point and stores it in value pt.

This also demonstrates the use of value parameters in ClassWithValParameter(val name: String), which automatically creates an internal property val name: String in the class:

class ClassWithValParameter(val name: String)
val aClass = new ClassWithValParameter("Gandalf")
aClass.name should be(res0)