Question

In Java, I am used to writing an abstract class that does some setup work and then delegates to the concrete class like this:

public abstract class Base {
    public void process() {
        // do some setup
        //...

        // then call the concrete class
        doRealProcessing();
    }
     
    protected abstract void doRealProcessing();
}

public class Child extends Base {
    @Override
    protected void doRealProcessing() {
        // do the real processing
    } 
}

I am having a hard time doing this in Ruby because I don’t have abstract classes or methods. I also read that "you aren’t supposed to need abstract classes or methods in Ruby and that I should stop trying to write Java in Ruby".

I would love to know what is the right way to implement the equivalence in Ruby?

Answer 1

Welcome to dynamically typed languages! You were probably nervous about just defining some function that wasn’t declared anywhere. Don’t be worried. It is very easy:

class Base
  def process
     # ...
     real_processing
  end

  def real_processing    # This method is optional!
    raise "real_processing not implemented in #{self.class.name}"
  end
end

class Child < Base
   def real_processing
     # ...
   end
end

b = Child.new
b.process

EDIT: Here’s another option for you which avoids the need to have two different method names:

class Base
  def process
    # ...
  end
end

class Child < Base
  def process
    # ...
    super   # calls the process method defined above in Base
    # ...
  end
end