[Rails] Re: why do I have to refer to my attr_accessible as self.varname?

On Dec 21, 6:12 pm, Dan Brooking <dmbrook...@gmail.com> wrote:

> class Page < ActiveRecord::Base
>   attr_accessible :url, :title
>
>   after_initialize :parse_page_params
>
>   def parse_page_params
>     @title = "test"
>   end
>
> and this wasn't working...  I understand what you said above about the
> instance variables, methods, initializing, etc.. but still a little unclear
> about why that code doesn't work as I'm setting it.  Is it because Rails
> uses the method name of title which hasn't been initailized in my
> assignment above?
>

Because rails doesn't use individual instance variables to store your
attributes (whether they've been marked as attr_accessible makes no
difference)

title = "foo"

Doesn't work because ruby assumes that you want to assign to the local
variable called title. Doing self.title = makes it clear that you want
to call the title= accessor

Fred

> On Fri, Dec 21, 2012 at 12:43 PM, Walter Lee Davis <wa...@wdstudio.com>wrote:
>
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> > On Dec 21, 2012, at 12:37 PM, Dan Brooking wrote:
>
> > > I posted a previous message about overriding initialize... because I was
> > having issues setting some of the parameters.  I have a Page model that has:
>
> > > attr_accessible :url, :title, :doc, :domain
>
> > > and it's called via:
>
> > > Page.new(:url => 'http://www.yahoo.com')
>
> > > Since I'm only passing in the url to new, I needed to set the other
> > parameters.  I was trying to do this via an after_initialize callback which
> > wasn't working so tried overriding initialize... still not working.
>
> > > What I found out was that in my after_initialize, I was referring to
> > title as @title which is why it was not working.  I switched it to
> > self.title and it works fine.
>
> > > My question is - why?
>
> > @title is an instance variable. Until you set it, it doesn't exist. Having
> > a method on the model called title (or an accessor, or some other Rails
> > magick) does not instantiate that method's return until and unless you ask
> > for it by calling the method. Calling self.method_name just makes it clear
> > which same-named method you really mean. Self is implied much of the time,
> > but when you have all the many method_missing options available, it might
> > not be the first one such that gets called.
>
> > Walter
>
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