From: "Tom V." <ruby-talk@...>
Date: 2007-05-07T18:06:22+09:00
Subject: Re: dynamically named variables or Constants

Hi Logan,

thanks for the hint.
However that did not get me too far.

So now I use simple instance variables 
and the session storage utility.

But I always get a strange error that let me to the idea
of using constants in the first place...

Although this is a rails project using a plugin,
the error I get is from using std ruby libraries.
so maybe you can enlighten me...
Please have a quick look:

Constructor for creating a new "live_tree":

class MyController
  # ...
  live_tree :fstree, :find_item_proc => 
            Proc.new { |x| FileSystemItem.new(x, @user_path) }
  # ...
end

class FileSystemItem
  def initialize(path, root)
    @path = path
    log << "root = #{root} - class = #{root.class}\n"
    # output:
    # root = /user/path/ - class = String

    @root = File.expand_path(root)
    # ERROR:
    # TypeError (can't convert nil into String):
    #  .//app/models/file_system_item.rb:17:in `expand_path'
    #  .//app/models/file_system_item.rb:17:in `initialize'
    #  .//app/controllers/my_controller.rb:452:in `new'
  end
end

"root" contains the user path and is of type String.
However, when calling File.expand_path,
I get the NameError.

When using a constant or a global variable
this error does not occur...

Any ideas?

Thanks for your time,
Tom.


On Mon, 7 May 2007 03:53:12 +0900
"Logan Capaldo" <logancapaldo@gmail.com> wrote:
> >         @new_constant = self::class::const_set(@constant_name,
> > @constant_value)
> >         logger.info("#{@new_constant}")
> >         # output: /path/to/nirvana
> >
> >         evaluate_constant = self::class::const_defined?(@new_constant)
> 
> should be self::class:const_defined?(@constant_name) of course.
> @new_constant is gonna hold the value of the constant, not the name.