As suggested in my thread in Ruby On Rails: Talk (http://
groups.google.com/group/rubyonrails-talk/browse_thread/thread/
66ae64e6581a3896) i'm posting an issue i'm having with Rails 2.0 and
overloading find_by methods here. Hoepfully someone can either suggest
what I am doing wrong and should be doing instead to get this working,
or tell me where to submit a bug report so this can get fixed if it is
not desired behaviour:
This came up when I migrated from rails 1.2.3 to 2.0.2. Previously, my
code was working fine. I am using
a mysql backend database, in which I am storing IPv4 addresses as 32
bit unsigned integers. Of course, I don't want my users to have to
enter the IP they are searching for in this fashion, nor do I want to
have to make the conversion myself every time I call the find_by_ip
function or find_or_create_by_ip function for the model, so I have
overloaded those two functions. find_by_ip now reads as follows:
def self.find_by_ip(ip)
super(NetAddr::CIDR.create(ip).to_i)
end
This works, the first time Ip.find_by_ip(address) is called (this test
done in script/console):
>> ip = Ip.find_by_ip("10.21.1.8")
=> #<Ip id: 13, ip: 169148680>
However any subsequent calls to find_by_ip just return nil, even for
the same IP address, until the environment is reloaded:
>> reload!
Reloading...
=> true
>> ip = Ip.find_by_ip("10.21.1.8")
=> #<Ip id: 13, ip: 169148680>
>> ip = Ip.find_by_ip("10.21.1.8")
=> nil
If I add some puts statements in my overloaded find_by_ip, they never
get printed out after the first call to it has been done. Equally, if
I call find_by_ip with a 32 bit int form of an IPv4 address it works
reliably:
def self.find_by_ip(ip)
puts "Testing\n"
super(NetAddr::CIDR.create(ip).to_i)
end
?> reload!
Reloading...
=> true
>> ip = Ip.find_by_ip("10.21.1.8")
Testing
=> #<Ip id: 13, ip: 169148680>
>> ip = Ip.find_by_ip("10.21.1.8")
=> nil
>> ip = Ip.find_by_ip(169148680)
=> #<Ip id: 13, ip: 169148680>
It is as if, after the first call to my overloaded find_by_ip, rails
decides to ignore my overloaded function and go straight to the base
functionality it has for creating find_by functions. The suggestion
was that, in Rails 2.0, instead of calling the method_missing function
every time I call super() from within a find_by_function (as there is
no specific find_by function of that name in ActiveRecord::Base), it
instead creates the find_by_ip function, which overwrites my one, and
subsequent calls hit that and thus don't get the IP address converted
to an int, and thus don't find any matching record in the database. I
am assuming this change was made for speed, as as long as you are not
overloading a find_by function it will be faster if the function is
pre-generated instead of having to be created every time it is called,
but what can I do to fix this? Is the best fix to call my 'overload'
function get_by_ip (or similar), so that the created find_by_ip
function doesn't have a namespace conflict, and then call
self.find_by_ip from within that once I have got my IP in numerical
format? This does work, but does mean that my code is sometimes using
find_by and sometimes using get_by (or whatever), which makes it
harder for anyone following to debug as it is not consistent.
Thanks
Dan Meyers
Network Support, Lancaster University
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