From: George Wang <stdcells@...>
Date: 2008-06-03T11:14:05+09:00
Subject: Re: Prevent ruby constant variables from changing?

Hi,

Thanks to everyone for their helpful replies.  Actually I want to be 
able to encapsulate a variable which is a Firefox browser instance.

I tried the following but to no avail.  Any ideas?

irb(main):001:0> require 'firewatir'
irb(main):002:0> include FireWatir
irb(main):003:0> module CONSTANT
irb(main):004:0> browser=FireWatir::Firefox.start('http://1.2.3.4/')
irb(main):005:0> end
irb(main):006:0> CONSTANT.constants
=>[]
irb(main):007:0> CONSTANT::browser
NoMethodError: undefined method 'browser' for CONSTANT::Module
        from (irb):7

George


Pe単a, Botp wrote:
> From: George Wang [mailto:stdcells@yahoo.com]
> # Is there a way I can fix the value that is initially assigned to the
> # constant variable?
> 
> arggh, ruby constants are global vars that croaks when you modify them 
> :)
> 
> i too had this problem, and the closest i can get is to wrap the 
> constants in a module and then freeze the module.
> 
> eg,
> 
> botp@botp-desktop:~$ irb
> 
> irb(main):001:0> module CONSTANT
> irb(main):002:1>   X=1
> irb(main):003:1>   Y=2
> irb(main):004:1>   Z="test"
> irb(main):005:1> end
> => "test"
> 
> irb(main):006:0> CONSTANT.constants
> => ["Z", "Y", "X"]
> 
> irb(main):008:0> CONSTANT::X
> => 1
> 
> irb(main):009:0> CONSTANT::X = 100
> (irb):9: warning: already initialized constant X
> => 100
> 
> irb(main):010:0> CONSTANT::X
> => 100
> 
> irb(main):011:0> CONSTANT.freeze
> => CONSTANT
> 
> irb(main):012:0> CONSTANT::X
> => 100
> 
> irb(main):013:0> CONSTANT::X = 99
> TypeError: can't modify frozen module
>         from (irb):13
>         from :0
> 
> irb(main):014:0> CONSTANT::X
> => 100
> 
> it's a blessing in disguise; i think i may stick to this scheme. 
> Considering how applications grow and how vars/constants clash, somehow 
> i feel like i should qualify my constants. It's safer, and readable too. 
> (and don't worry, there is no unfreeze in ruby ;)
> 
> kind regards -botp

-- 
Posted via http://www.ruby-forum.com/.