From: Logan Capaldo <logancapaldo@...>
Date: 2007-07-20T19:35:23+09:00
Subject: Re: enumeration with symbol name information

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On 7/20/07, Sasa <sasa555@gmail.com> wrote:
>
> Hello everybody...
> I have a beginne's question:
>
> I've created class for my numeric constants, it looks like:
>
> class MyClass
>
>   NAME1 = 0
>   NAME2 = 1
>   NAME3 = 2
>   #etc...
>
>   def self.to_s(something)
>     case something
>       when 0
>         "NAME1"
>       when 1
>         "NAME2"
>       when 2
>         "NAME3"
>       #etc...
>     end
>   end
>
> end
>
>
> What is more elegant way to do this? Basically, I want to convert the
> numerical value to string representation (ideally via identifier name).


In ruby we often use symbols in place of of enumerations. Any place you'd
use  NAME0, use :name0.  For NAME1 use :name1, etc.

For example:
class MyClass
  def something
     case @enum_value
     when :name0
         puts "In name zero mode"
     when :name1
         puts "In name one mode"
     end
  end
end

:name0.to_s #=> "name0"

If, for whatever reason you don't want to use symbols, a way I occasionally
use to emulate enums is the following:

NAME0 = Object.new

def NAME0.to_s
   "NAME0"
end

NAME1 = Object.new

def NAME1.to_s
   "NAME1"
end

...


Another method that could be used to simplify your existing code is to use a
hash:

NAME0 = 0
NAME1 = 1
NAME2 = 2

Names = { NAME0 => "NAME0", NAME1 => "NAME1", NAME2 => "NAME2" }

def self.to_s(something)
   Names[something]
end

You can even wrap this one up (or the previous method with some
metaprogramming:)

def self.enum(*args)
   const_set("Names", {})
   args.each_with_index do |v, i|
      Names[i] = v
      const_set(v, i)
   end
end

enum "NAME0", "NAME1", "NAME2"


Thanks in advance,
> Sasa
>
>
>
>

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