On 28/01/2009, at 12:12 PM, Pat Maddox wrote:
On Wed, Jan 28, 2009 at 8:30 AM, Nick Hoffman <n...@deadorange.com>
wrote:
On 28/01/2009, at 7:50 AM, Zach Dennis wrote:
On Tue, Jan 27, 2009 at 2:48 PM, Nick Hoffman
<n...@deadorange.com> wrote:
G'day folks. I've been beating my head on this one problem for a
couple
of
hours, and have managed to figure out what's causing it. However,
I don't
understand why it's happening, nor do I know how to solve or get
around
it.
One of my methods clones an arg, and it seems that doing so
causes state
to
leak out. I discovered this because changing this:
new_subtitle = subtitle.clone
to this:
new_subtitle = subtitle
causes the problem to disappear.
Before we get into the code snippets, are there any known caveats,
warnings,
or problems with writing specs that cover the cloning or
duplication of
objects?
Here's the code, specs, and spec output:
http://gist.github.com/53482
As you can see, in the "should clone ..." example, the
expectation on
line
24 succeeds, but the same expectation on line 28 fails. After
that, the
same
expectation fails in the "should not leak state" example.
What does your full SubtitleFile class look like? It looks like
there
is an issue with how the #subtitles method is storing information.
Since you're using ActiveRecord::BaseWithoutTable there are probably
not going to be any unique primary keys amongst your SubtitleFiles
to
help differentiate them. So if #subtitles is a has_many, every
call to
SubtitleFile#subtitles may lookup Subtitles in the exact same way
w/o
any unique key to use to differentiate which subtitles belong to
which
subtitle files which would produce the results you are seeing.
Is Subtitle a ActiveRecord::BaseWithoutTable or a real
ActiveRecord::Base
model?
Hi Zach. Subtitle is an ActiveRecord::BaseWithoutTable model; it
does not
inherit from ActiveRecord::Base .
The SubtitleFile "subtitles" attribute is actually just an Array. I
didn't
bother to setup a has_many relationship with Subtitle.
SubtitleFile#subtitles is a standard getter method that
ActiveRecord sets up
for me.
In my app's console, I tested out a has_many relationship between two
ActiveRecord::BaseWithoutTable models, and there weren't any mixups
after
creating associations between different model instances.
Here's the source for the SubtitleFile model. The #add_subtitle! in
question
starts on line 74:
http://gist.github.com/54028
I'm not familiar with this library, so I can't say for sure, but the
line
default :subtitles => []
looks very suspicious to me.
The underlying library code would have to do a .clone of that default
value, otherwise all instances will share the same array (meaning if
you push a value onto it, the next instance will have that array with
one element).
If it doesn't automatically clone (it may, I don't know), it probably
should provide a lambda syntax so you can do:
default :subtitles => lambda { [] }
Pat
Pat, the lambda fixed the problem. That's a keen spidey sense you have
there!
To spell this out in more detail, having
defaults :subtitles => []
causes the SubtitleFile class to initialise an Array when the class is
defined. From then on, the "subtitles" attribute of all SubtitleFile
instances will refer to that one specific array.
Thanks for your help with this, mate. It's much appreciated.
Nick
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