From: Gary Wright <gwtmp01@...>
Date: 2007-11-02T02:54:50+09:00
Subject: Re: use of case statement doesn't work as I expected, what am I doing wrong?


On Nov 1, 2007, at 12:36 PM, Gabriel Dragffy wrote:
> I have an object ( a website tester) that can return various  
> values. One of which is Net:HTTPOK, I want to use a case statement  
> to evaluate this and set a variable called 'severity', as follows:
>
> result = TestWebsite::test( site )
> case result
> when Net::HTTPOK
> severity = :INFO
> when SocketError
> severity = :ERROR
> else
> severity = :WARN
> end
>
> However, when Net::HTTPOK is returned, the severity variable ALWAYS  
> ends up as :WARN instead of :INFO.

There are two issues:

1) case uses the === operator and not ==

This means that the comparisons in your case statement are:

	Net::HTTPOK  === result
	SocketError  === result

2) Class#=== doesn't test for equality.  It checks to see if
    the argument is an instance of the class, which is not
    true in your case, Net::HTTPOK is not an instance of itself.

Just to be clear, Net::HTTPOK and SocketError are class objects
(instances of Class) and so they use Class#=== in case statements.

You could rewrite your case as an if/then/else or use the alternate
form of the case statement:

   case
   when result == Net::HTTPOK
     severity = :INFO
   when result == SocketError
     severity = :ERROR
   else
     severity = :WARN
   end

There of course lots of other possibilities:

   severity_map = Hash.new(:WARN).merge(Net::HTTPOK => :INFO,  
SocketError => :ERROR)

   severity = severity_map[TestWebsite::test(site)]

Gary Wright