From: William Djaja Tjokroaminata <billtj@...>
Date: 2002-04-12T23:17:45+09:00
Subject: Why Object#class Is Inconsistent in "==" and "case"?

Hi,

I know that when I use the case statement, it is the "===" operator that
is actually being used.  However, the behavior with respect to
Object#class is so inconsistent between "==" and "===".  For example,

    module MyModule
      class MyClass
      end

      obj = MyClass.new

      puts "Using == it is OK" if obj.class == MyClass

      case obj.class
      when MyClass
        puts "Using case it is OK too"
      when MyModule::MyClass
        puts "Using case has to use the module name"
      else
        puts "The class name is #{obj.class}"
      end

      case obj.class.name
      when 'MyModule::MyClass'
        puts "Using case has to use the module and class names"
      end
    end

So when I am using "==", it is very easy.  However, when I use the case
statement there are two extra work that I have to do:

1) Use the object class name instead of simply the object class.
2) Add the class module name instead of simply using the class name, even
though I am inside the very same module.

To me, this is a kind of violation of the Priciple of Least Surprise.  Is
there any particular reason why Ruby behaves like this?  With this
behavior, I am tempted to use the if...elsif...elsif...else construct when
dealing with Object#class instead of the more elegant case statement.

Regards,

Bill