From: "David A. Black" <dblack@...>
Date: 2009-01-21T11:47:51+09:00
Subject: Re: cannot get attr_accessor to work

Hi --

On Wed, 21 Jan 2009, Tom Cloyd wrote:

> David A. Black wrote:
>> Hi --
>> 
>> On Wed, 21 Jan 2009, Tom Cloyd wrote:
>> 
>>> I've been staring at this for a couple of hours, and I cannot crack the 
>>> nut. This SHOULD work, but I'm obviously screwing up. Just cannot see 
>>> where. I'm carefully following several examples, but...I cannot get access 
>>> to my instance variables.
>>> 
>>> Here's a stripped down version of the code -
>>> 
>>> # SetNet.rb
>>> 
>>> def main
>>> # Set up logging
>>> run_log = Manage_log.new( 'logfile.txt' ).open
>>> log = run_log.log
>>> logging_now = run_log.lgg    # @logging_now = false
>> 
>> I haven't read the rest of your code but I'll bet the problem is right
>> there. Ruby is interpreting log and logging_now as local variables. If
>> you want to call the methods of those names, you have to do:
>>
>>   self.log = run_log.log
>>   self.logging_now = run_log.lgg
>> 
>> Basically, given any expression that looks like this:
>>
>>    var = value
>> 
>> the parser interprets var as a local variable name. So you have to add
>> the explicit receiver to achieve the method call.
>> 
>> 
>> David
>> 
> David,
>
> Thank for your reply, but I'm puzzled by it. Doesn't the code in my previous 
> post make it clear that I'm dealing with instance variables? The class 
> instance initiates them, e.g., @log, and I'm trying to get that with the 
> run_log.log call. This is NOT an attempt to call a method. I very carefully 
> copied (I thought) the pattern I saw in several authoritative sources, but it 
> doesn't work for me, which is nuts.
>
> I hope this makes sense.

The code I saw was:

>>> run_log = Manage_log.new( 'logfile.txt' ).open
>>> log = run_log.log
>>> logging_now = run_log.lgg    # @logging_now = false

which are local variable assignments, and you'd mentioned
attr_accessor, so I assumed you had attr_accessor somewhere in a part
of the code you hadn't posted. It's a common error to do:

   class C
     attr_accessor :name
     def initialize(name)
       name = name        # should be @name or self.name
     end
   end

so I surmised that that was what was going on. Oh well -- can't hurt
to see that particular potential problem anyway :-)

I'm still not sure where attr_accessor fits in.


David

-- 
David A. Black / Ruby Power and Light, LLC
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