From: Brian Candler <b.candler@...>
Date: 2010-07-07T21:40:40+09:00
Subject: Re: Ruby switches

Kenneth     wrote:
> Let's say I have something like this
> 
> case
> when "".empty?        then puts "Empty"
> when "".nil?          then puts "Nil"
> when "".include?("a") then puts "Includes 'a'"
> end
> 
> Is there a way to do something like this instead? (This does not work
> since the methods in the switches are acting on Object instead of "".)
> 
> case ""
> when empty?        then puts "Empty"
> when nil?          then puts "Nil"
> when include?("a") then puts "Includes 'a'"
> end

case str
when "": puts "Empty"
when nil: puts "Nil"
when /a/: puts "Includes 'a'"
end

The case statement actually expands to the === operator, so this is 
equivalent to

if "" === str
  puts "Empty"
elsif nil === str
  puts "Nil"
elsif /a/ === str
  puts "Includes 'a'"
end

The === operator does the "right thing" in each of these cases.
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