Ruby - Protected and Private Methods in Descendant Classes

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Introduction

The following code created a MyClass object called myob and a MyOtherClass object, myotherob, where MyOtherClass descends from MyClass: 

class MyClass
    private
        def priv( aStr )
            return aStr.upcase
        end
    protected
        def prot( aStr )
            return aStr << '!!!!!!'
        end
    public
        def exclaim( anOb )  # calls a protected method
            puts( anOb.prot( "This is a #{anOb.class} - hurrah" ) )
        end
        def shout( anOb )    # calls a private method
            puts( anOb.priv( "This is a #{anOb.class} - hurrah" ) )
        end
end
class MyOtherClass < MyClass
end
class MyUnrelatedClass
end

myob = MyClass.new
myotherob = MyOtherClass.new
myunrelatedob = MyUnrelatedClass.new

myob.shout( myotherob )     # fails

Here the shout method calls the private method priv on the argument object: 

def shout( anOb )    # calls a private method
   puts( anOb.priv( "This is a #{anOb.class} - hurrah" ) )
end

This won't work! The priv method is private. 

myotherob.shout( myob )     # fails

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