Model.find_by_attribute only called the first time

[Hiro Protagonist]

# This is a sanitized example of what I am doing at work and was
perplexed

def Person.find_by_name(*params)
puts "hello world!"
params.first.chop! if params.first.last == "."
super
end

# It strips the trailing . and puts hello world!
>> Person.find_by_name("Chris.")
"hello world!"
=> #<Person id: 1, :name: "Chris">

# I hit up arrow and enter

=> nil

# Why is the method not actually being called the second time?
# I can handle never working and always working, but always working
once I can't handle.

Thanks,
Chris Lundquist

[Ryan Bigg]

May I suggest aliasing the method instead of trying to call super?

alias_method :old_find_by_name, :find_by_name

def Person.find_by_name(*params)

  params.first.chop! if params.first.last == "."

  old_find_by_name(params)

end

2009/11/10 Hiro Protagonist <rampant...@gmail.com>

--
Ryan Bigg

[Michael Koziarski]

> May I suggest aliasing the method instead of trying to call super?
> alias_method :old_find_by_name, :find_by_name
> def Person.find_by_name(*params)
>   params.first.chop! if params.first.last == "."
>   old_find_by_name(params)
> end

super won't work here because the method isn't defined on a parent of
Person, it's defined on person itself. So what's happening is that
the call to method missing is generating a *new* implementation of
find_by_name which simply does the find, without your changes.

We could fix this for rails 3.0 by moving those generated methods from
Person to a module included in person, but for 2.3 you'll have to do
as Ryan suggests and use aliasing, or just call
all(:conditions=>{:first_name=>params.first}) instead of super.

--
Cheers

Koz

[Hiro Protagonist]

Koz and Ryan,

Now that you point it out, I see how #method_missing calls find, then
find thinks I'm retarded and over writes my method by doing a class
eval. Thus removing my original code.

Am I figuring that right?

I've always had trouble generating aliases to singleton methods.

I seem to recall the following syntax doesn't work
alias self.old_name self.new_name

but I might be confusing trying

alias old_name self.new_name

Thank you for your insights,
Chris Lundquist

[Ryan Bigg]

I've just realised that because this is a dynamic finder the "power" of method_missing is what's going to stop you from being able to alias this method. This method appears to not be defined until method_missing catches it and defines it then. I've tried also calling the method before aliasing it (thereby defining it) but without much luck:

user.rb:

find_by_name(nil)

  

  class_eval do 

    alias_method :old_find_by_name, :find_by_name

  end

NameError: undefined method `find_by_name' for class `User'

I'm really interested in how this would be done now.

2009/11/10 Hiro Protagonist <rampant...@gmail.com>

--
Ryan Bigg

[Hiro Protagonist]

I just wanted a :before_find hook, saw the mail history from here
during 2006 and they said do

def find
# Before Find.
super
# After Find
end

But now we know how that turns out.

Ultimately it isn't important to my app, but it would be nice when me
or users forget trailing .s

Thanks,
Chris Lundquist

On Nov 9, 3:23 pm, Ryan Bigg <radarliste...@gmail.com> wrote:
> I've just realised that because this is a dynamic finder the "power" of
> method_missing is what's going to stop you from being able to alias this
> method. This method appears to not be defined until method_missing catches
> it and defines it then. I've tried also calling the method before aliasing
> it (thereby defining it) but without much luck:
>
> user.rb:
>
> find_by_name(nil)
>
>   class_eval do
>     alias_method :old_find_by_name, :find_by_name
>   end
>
> NameError: undefined method `find_by_name' for class `User'
>
> I'm really interested in how this would be done now.
>

> 2009/11/10 Hiro Protagonist <rampantduran...@gmail.com>

[Matt Jones]

On Nov 9, 2009, at 7:06 PM, Hiro Protagonist wrote:

>
> I just wanted a :before_find hook, saw the mail history from here
> during 2006 and they said do
>
> def find
> # Before Find.
> super
> # After Find
> end
>
> But now we know how that turns out.
>
> Ultimately it isn't important to my app, but it would be nice when me
> or users forget trailing .s
>

You might also want to think about doing this in a before_filter;
cleaning trailing spaces off of request parameters feels pretty
controller-y to me.

--Matt Jones

[Hiro Protagonist]

I'm working with BIND files and DNS. Sometimes the method isn't called
from a controller. Sometimes it will be called from a cron tab and
script/runner