From: Robert Klemme <shortcutter@...>
Date: 2009-04-08T01:04:09+09:00
Subject: Re: barenames and case statements

On 07.04.2009 17:21, LAMBEAU Bernard wrote:
> Because the === operator of the Class class (used in case statements)
> checks for 'is an instance of'.
> 
> So, the following:
> 
>>    case klass
>>    when String
>>        puts "String!"
>>    end
> 
> is to be interpreted as String===klass, that is to,
> klass.is_a?(String), which is false. But the following is true:
> 
> case klass
> when Class
>   puts 'It's a class of course'
> end

A solution would be to use the other form of "case":

[String, Array, Hash].each do |klass|
     case
     when klass == String
         puts "String!"
     when klass == Array
         puts "Array!"
     when klass == Hash
         puts "Hash!"
     else
         puts "I don't know: #{klass}"
     end
end

Or encapsulate tests in a special instance:

IsString = Object.new
def IsString.===(c)
   String == c
end

klass = String

case klass
when IsString
   puts "Ah!"
end


Kind regards

	robert