Scala standalone object not getting recognized - scala

Question

I am creating a singleton object using script xyz.scala as follow :
object ChecksumCalculator {
def calcChecksum(s: String): Int = {
val cc = new ChecksumCalculator
for (c <- s)
cc.add(c.toByte)
cc.checksum
} }
When I run this as script as Scala xyz.scala ,
I am getting the error as :
01HW993798:scala tcssig$ scalac xyz.scala
xyz.scala:3: error: not found: type ChecksumCalculator
val cc = new ChecksumCalculator
^
one error found
Although I have declared the standalone object at the top, is it possible that my standalone object is not getting recognized.
Or is it due to some other error ?

Answer 1

In scala, singleton objects are instantiated on usage and guaranteed to be instantiated only once, hence providing strict "singleton" semantics.
Assuming that your object has method "add(b:Byte)" you could do:
CheckSumCalculator.add(c.toByte)
But given that we are in the scope of CheckSumCalculator, using this should be sufficient:
add(c.toByte)
That said, using a singleton object for mutable operations seems a bad idea.
It looks like that what you are looking for is to create instances of some class, but also have some facility method that can be called statically.
That construction has a name in Scala: A companion object
companion objects are defined by creating an object of the same name as some given class.
Translating that to this scenario, we would have:
class ChecksumCalculator {
def add(b:Byte) = ???
def checksum(): Int = ??? // or whatever type the checksum is
}
object ChecksumCalculator { // this is a companion object
def calcChecksum(s: String): Int = {
val cc = new ChecksumCalculator
s.foreach(c => cc.add(c.toByte))
cc.checksum()
}
}