Question

I think ‘object’ in Scala is pretty similar to Singleton in Java which is not considered to be a good design practice. Singleton to me is like another way to define global variables which is BAD. I wrote some Scala code like this because it’s easy and it works but the code looks ugly:

object HttpServer { // I'm the only HttpServer instance in this program.
  var someGlobalState: State
  def run() {
    // do something
  }
}

I’m trying to avoid doing this. When is it good to define Scala object?

Answer 1

No. Many Scala-Libraries heavily rely on object.

The main goal of the Singleton-Pattern is that just one instance of the Object can exist. The same holds true for Object.

You may misuse it as global variable but that is not the point.

Object are for example a great place for Factory Methods or a replacement for Modules to hold functions.