I am at the early stages of learning Scala and I've noticed different ways to declare methods.
I've established that not using an equals sign makes the method a void method (returning a Unit instead of a value), and using an equals sign returns the actual value so
def product(x: Int, y: Int) {
x*y
}
will return () (Unit), but
def product(x: Int, y: Int) = {
x*y
}
will return the product of the two arguments(x*y)
I've noticed a third way of declaring methods - with a colon. Here is an example
def isEqual(x: Any): Boolean
How does this differ from the = notation? And in what situations will it be best to use this way instead?
When you use colon (and use equal) you explicitly define return type of method.
// method return Boolean value
def m(a : Int) : Boolean = a > 0
When you don't use colon and use equal you allow scala compiler inferring return type itself.
// method has return type of last expression (Boolean)
def m(a : Int) = a > 0
When you use neither colon nor equal your method has return type of Unit class.
// method has Unit return type
def m(a : Int){
a > 0
}