From: Johan Eriksson <johan@...>
Date: 2008-04-27T01:50:42+09:00
Subject: Re: undefined local variable

Johan Eriksson wrote:
> Hi --
> 
> David A. Black wrote:
>> Hi --
>>
>> On Sat, 26 Apr 2008, Johan Eriksson wrote:
>>
>>> 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.
>>
>> Can you give some sample YAML input? I'm still not quite picturing it.
>>
>>
>> David
> 
> This is a simple example:
> 
> dogs:
>     - name        : Fido
>       age         : 2
> 
>     - name        : Rufus
> 
>     - name        : Doggie
>       age         : 4
> 
>     - name        : Puppy
>       age         : 1
> 
> The function should then create four instances of dog, assign them the 
> names and ages specified, put them in a list and return them.
> 
> Thanks for taking the time to help me out!
> 
> /Johan
> 
> 
> 

No ideas, anybody? I really don't see why it does not find the variable 
there, as it finds it in if-statement.

/Johan