Companion objects in scala - scala

Question

can any one explain the following output. I have a simple Scala code like this..
object compOrNotTest {
def main(args: Array[String]) {
var emp = new Employee("tom", 20)
println(emp)
println(Employee.adult(emp))
Employee.printName("Roland", 38)
var emp2 = new Employee("Harry", 37)
Employee.printName(emp2)
}
}
class Employee(name: String, age: Int) {
val ageOfEmplyedd: Int = age
val nameEmp: String = name
override def toString() = this.name + " age : " + this.age
def printName() {
println("name is in Class " + nameEmp)
}
}
object Employee {
def adult(emp: Employee) = {
if (emp.ageOfEmplyedd > 18)
true
else
false
}
def printName(name: String, age: Int) = {
val emp1 = new Employee(name, age)
println("Name is : " + emp1.printName())
}
def printName(emp1: Employee) = {
//val emp1 = new Employee(name, age)
println("Name is : "+ emp1.printName())
}
}
And the output I am getting is
tom age : 20
true
name is in Class Roland
Name is : ()
name is in Class Harry
Name is : ()
My question is that why , when I am calling from Companion object I am getting only Name is : (). I am expecting something like Name is : name is in Class Roland. Please help me out to understand the how scala works in this case. Thanks a lot

Answer 1

The return type of Employee.printName (in class Employee) is Unit. This is because this function was declared using procedure syntax (a function declaration with no = sign in it, which has been deprecated and which will no longer be supported in a future version of Scala) that has an associated return type of Unit. The Unit value that is returned is represented in Scala as ().
The following function declarations are equivalent:
// Using (soon-to-be-deprecated) procedure syntax.
def printName() {
println("name is in Class " + nameEmp)
}
// Using an explicit return type.
def printName(): Unit = {
println("name is in Class " + nameExp)
}
// Using an inferred return type (note "=" in declaration). The last statement is the call
// to println, which returns Unit, so a return type of Unit is inferred.
def printName() = {
println("name is in Class " + nameExp)
}
If you wanted to return the string that was printed, you would need something like this:
def printName() = {
val s = "name is in Class " + nameEmp
println(s)
s
}
Or, using an explicit return type, instead of inferring it from the last statement:
def printName(): String = {
val s = "name is in Class " + nameEmp
println(s)
s
}