From: Kjell Olsen <kjell@...11.net>
Date: 2007-02-23T11:23:03+09:00
Subject: Re: Ruby's "case" doesn't behave like a normal switch

Check this out for making your case statements work:

http://redhanded.hobix.com/bits/wonderOfTheWhenBeFlat.html

"Consider Olympic ice dancing out-graced!"

-kjell

On Feb 22, 2007, at 7:55 PM, Guillaume Nargeot wrote:

> The problem with ruby is that you can't use a switch as it behaves  
> with many
> other languages like C, php, etc.
>
> For example, you want to convert the following peace of code to ruby:
>
> switch (x) {
>   case 1:
>   case 2:
>     # do something
>     break;
>   case 3:
>     # do some other thing
>     break;
>   default:
> }
>
> it seems you can do it with the following code:
>
> case x
>   when 1..2
>     # do something
>   when 3
>     # do some other thing
>   else
> end
>
> But when it comes to strings, you would like to be able to do simply:
>
> case x
>   when "this"
>   when "that"
>     # do something common to "this" and "that"
>   when "nothing"
>     # something different
> end
>
> The problem is that you can't, because of the fact the "break" is  
> implicit
> in
> the ruby language.
> The fact is that you don't want to rewrite the same code two times.
> Of course, you would be able to right your code into a function,  
> and then
> just
> write:
>
> case x
>   when "this"
>     func_this_that()
>   when "that"
>     func_this_that()
>   when "nothing"
>     # something different
> end
>
> But if again, you don't want to relay on a function call, here's a  
> solution
> I thought about.
>
> This is not perfect, because you have to change your syntax, but it  
> might be
> quite useful in some cases.
>
> # Redefine the === method of the Array class, that is used to match  
> the
> argument
> # of the "case" directive.
> class Array
>   # Return true if self contains any element of the given parameter.
>   def ===(o)
>     o.each do |e|
>       return true if self.include?(e)
>     end
>     false
>   end
> end
>
> # Example 1
> x = ["case4"]
>
> case x
>   when ["case1", "case2"]
>     puts "first case"
>   when ["case3", "case4", "case5"]
>     puts "second case"
>   when ["case6"]
>     puts "third case"
>   else
>     puts "not matched"
> end
>
> # Returns: "second case"
>
> # Example 2
> x = [6]
>
> case x
>   when [1, 2]
>     puts "first case"
>   when [3, 4, 5]
>     puts "second case"
>   when [6]
>     puts "third case"
>   else
>     puts "not matched"
> end
>
> # Returns: "third case"
>
> What do you think about it ?
>