From: Johan Eriksson <johan@...>
Date: 2008-04-26T03:45:00+09:00
Subject: Re: undefined local variable

Hi --

David A. Black wrote:
> Hi --
> 
> On Sat, 26 Apr 2008, Johan Eriksson wrote:
> 
>> Chris Hulan wrote:
>>> On Apr 25, 11:16 am, Johan Eriksson <jo...@johaneriksson.se> wrote:
>>>> Hi!
>>>>
>>>> I have some troubles with this.
>>>>
>>>>            obj_as_list.each do |att|
>>>>              if att[1].is_a?(String)
>>>>                att[1] = "'#{att[1]'"
>>> You're missing a '}' here ----------^
>>>
>>> does that help?
>>>
>>
>> Nope. I am providing the surrounding function here. (It is defined 
>> inside a class.)
>>
>>    def load_from_file(filename)
>>      require 'yaml'
>>      yaml_dict = YAML::load(File.open(filename))
>>      object_list = []        #The list that should be returned
>>      yaml_dict[yaml_dict.keys[0]].each do |yaml_obj|
>>        new_obj = self.class.new
>>        yaml_obj.each do |obj|
>>          obj_as_list = obj.to_a
>>          obj_as_list.each do |att|
>>            if att[1].is_a?(String)
>>              att[1] = "'#{att[1]}'"
>>            end
>>            str = "new_obj.#{att[0]} = #{att[1]}"
>>            eval(str)
>>          end
>>        end
>>        object_list << new_obj
>>      end
>>      object_list
>>    end
>>
>> And the error:
>>
>>     NameError: undefined local variable or method `att' for main:Object
> 
> If att[1] is, say, :att, then "#{att[1]}" is "att" and you've got a
> dangling att. The whole eval thing seems extremely fragile (which eval
> things usually are). I imagine there's a more robust and probably
> shorter way to do this, but I'm not sure what the data coming in and
> out are supposed to be like.
> 
> 
> David
> 

I am almost positive that there is, given that I'm pretty much a noob at 
ruby. The whole thing is a class_eval too. The idea is to add this 
function to a class that has just been created based on a textfile. The 
function will receive a file that includes a yaml description of 
instances of the class, and the function then makes these instances and 
sends them back as a list. I think some fragility is okay, though I'd be 
keen on learning better ways to do this. Around the entire function is

the_class.class_eval %{
	the function...
}

I am confused about why it doesn't work though.

/Johan