Rails - Aug 2007 - Chaining validate method in a plugin, completely stumped

I''m trying to write a plugin which adds some new logic to the validate
method of an ActiveRecord model.  However, I still want the user to be
able to define their own validate method in the model, and to call
that as well as my new validate method.  What''s happening now is if I
define a validate method and the user defines a validate method as
well, the validate method defined by the user will be called and the
method in my plugin will not be called.

I''ve tried to use alias_method to install my validate method in the
place of the previous validate method, while still allowing me to call
the original method as follows:

alias_method :orig_validate, :validate
alias_method :validate, :new_validate

but when I place this after my validate method definition in my
plugin, I get the following error when starting my server:

undefined method `validate'' for module
`AttachmentHandler::InstanceMethods''

I need to instruct rails that I''m redefining the validate method from
ActiveRecord::Validations::ClassMethods but I don''t know how to do
this.

My end goal is to be able to add some conditions that a model must
satisfy before being saved, and if it doesn''t pass these conditions,
then I need to add errors to the object.  If there''s a better way to
do this than overriding validate, that would also be an option.. But
right now, I''m completely stuck and can''t figure this out. Any
help
would be greatly appreciated.  Thanks,

Mike

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Mike Garey wrote:
> My end goal is to be able to add some conditions that a model must
> satisfy before being saved, and if it doesn''t pass these
conditions,
> then I need to add errors to the object.  If there''s a better way
to
> do this than overriding validate, that would also be an option.. But
> right now, I''m completely stuck and can''t figure this
out. Any help
> would be greatly appreciated.  Thanks,
How about adding a before_validation or after_validation callback.


-- 
We develop, watch us RoR, in numbers too big to ignore.


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On 8/24/07, Mark Reginald James
<mrj-bzGI/hKkdgQnC9Muvcwxkw@public.gmane.org>
wrote:
>
> Mike Garey wrote:
>
> > My end goal is to be able to add some conditions that a model must
> > satisfy before being saved, and if it doesn''t pass these
conditions,
> > then I need to add errors to the object.  If there''s a better
way to
> > do this than overriding validate, that would also be an option.. But
> > right now, I''m completely stuck and can''t figure
this out. Any help
> > would be greatly appreciated.  Thanks,
>
> How about adding a before_validation or after_validation callback.
if I use before_validation, the errors that I add are not carried
through to when the validate method is called.  If I return false from
my before_validation method, the error messages added are available,
but the validate method is not called (I guess returning false in
before_validate halts the filter chain).  If I use after_validation,
the errors are added to the object, but the object is still allowed to
be saved, even if I return false in after_validation.

So it doesn''t look like I can use the before/after validation
callbacks (and also, are these callbacks chained? ie if I defined my
own before/after validation, and the user defines their own as well,
won''t their definition override mine?)

Thanks,

Mike

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Mike Garey wrote:
> if I use before_validation, the errors that I add are not carried
> through to when the validate method is called.  If I return false from
> my before_validation method, the error messages added are available,
> but the validate method is not called (I guess returning false in
> before_validate halts the filter chain).  If I use after_validation,
> the errors are added to the object, but the object is still allowed to
> be saved, even if I return false in after_validation.
Yes, you''re right. Neither before_validation nor after_validation
will give you what you want.
> So it doesn''t look like I can use the before/after validation
> callbacks (and also, are these callbacks chained? ie if I defined my
> own before/after validation, and the user defines their own as well,
> won''t their definition override mine?)
No, callbacks are properly chained.

You can get your alias_method calls to work if you call them
on the user class after your module has been included, either in
the module "included" method or after the include statement
in your capability-adding method.

-- 
We develop, watch us RoR, in numbers too big to ignore.


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On 8/24/07, Mark Reginald James
<mrj-bzGI/hKkdgQnC9Muvcwxkw@public.gmane.org>
wrote:
>
> Mike Garey wrote:
> You can get your alias_method calls to work if you call them
> on the user class after your module has been included, either in
> the module "included" method or after the include statement
> in your capability-adding method.
yeah, I noticed that works fine, but since this is a plugin, I wanted
to make this as invisible as possible.. Requiring the user to add the
alias_method_chain calls after they define their own validate method
is more obtrusive than I wanted.  Since this is the ruby/rails world,
I figured there would have to be a better way, but unfortunately I
can''t figure it out.

It''s a bit of a catch-22.. I can''t use alias_method in my
plugin,
since the plugin is loaded before the entire User class is loaded,
which means that the validate method isn''t available to be aliased..
I wish there was a way of telling rails to alias the method
regardless, under the assumption that the method will be available.
Or to figure out some other way to hook into the validation class.

Thanks for the response Mark,

Mike

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Mike Garey wrote:
> On 8/24/07, Mark Reginald James
<mrj-bzGI/hKkdgQnC9Muvcwxkw@public.gmane.org> wrote:
>> Mike Garey wrote:
>> You can get your alias_method calls to work if you call them
>> on the user class after your module has been included, either in
>> the module "included" method or after the include statement
>> in your capability-adding method.
> 
> yeah, I noticed that works fine, but since this is a plugin, I wanted
> to make this as invisible as possible.. Requiring the user to add the
> alias_method_chain calls after they define their own validate method
> is more obtrusive than I wanted.  Since this is the ruby/rails world,
> I figured there would have to be a better way, but unfortunately I
> can''t figure it out.
> 
> It''s a bit of a catch-22.. I can''t use alias_method in my
plugin,
> since the plugin is loaded before the entire User class is loaded,
> which means that the validate method isn''t available to be
aliased..
> I wish there was a way of telling rails to alias the method
> regardless, under the assumption that the method will be available.
> Or to figure out some other way to hook into the validation class.
By putting it in your capability-adding method i meant:

module ActsAsMike
   module ClassMethods
     ...
   end

   module InstanceMethods
     def new_validate
      ...
      validate # Call AR::B validate or UserClass validate
     end
     ...
   end
end

class ActiveRecord::Base
   def self.acts_as_mike
     extend ActsAsMike::ClassMethods
     include ActsAsMike::InstanceMethods
     alias_method :orig_validate, :validate
     alias_method :validate, :new_validate
   end
end



-- 
We develop, watch us RoR, in numbers too big to ignore.


--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On 8/24/07, Mark Reginald James
<mrj-bzGI/hKkdgQnC9Muvcwxkw@public.gmane.org>
wrote:
> By putting it in your capability-adding method i meant:
>
> module ActsAsMike
>   module ClassMethods
>     ...
>   end
>
>   module InstanceMethods
>     def new_validate
>      ...
>      validate # Call AR::B validate or UserClass validate
>     end
>     ...
>   end
> end
>
> class ActiveRecord::Base
>   def self.acts_as_mike
>     extend ActsAsMike::ClassMethods
>     include ActsAsMike::InstanceMethods
>     alias_method :orig_validate, :validate
>     alias_method :validate, :new_validate
>   end
> end
>
thanks for the respone Mark, I seem to be getting closer, as I can now
override the default validate method and still call the original
validate method from within new_validate.  The only problem is that
the user _must_ place the ''acts_as_validatable'' class method
after
their validate method, otherwise the alias_method call won''t override
their method, and my new_validate method will not be called.  Ideally,
I''d like to avoid having the restriction that the user must call
acts_as_validatable after they define their own validate method - is
there any way to get around this?

Here''s the minimal code for the plugin I''ve got right now:

acts_as_validatable.rb
module ActsAsValidatable
  module InstanceMethods
    def new_validate
      logger.warn("NEW VALIDATE CALLED")
      orig_validate
    end
  end
end

# ActsAsValidatable
class ActiveRecord::Base
  def self.acts_as_validatable
    include ActsAsValidatable::InstanceMethods

    alias_method :orig_validate, :validate
    alias_method :validate, :new_validate
  end
end

the following works perfectly (the logger shows both "NEW VALIDATE
CALLED" and then "ORIGINAL VALIDATE CALLED")

my_class.rb
class MyClass < ActiveRecord::Base
  def validate
    logger.warn("ORIGINAL VALIDATE CALLED")
  end

  acts_as_validatable
end

the following doesn''t work (the only thing that gets logged is
"ORIGINAL VALIDATE CALLED"):

my_class.rb
class MyClass < ActiveRecord::Base
  acts_as_validatable

  def validate
    logger.warn("ORIGINAL VALIDATE CALLED")
  end
end

Thanks again for the help,

Mike

--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Ruby on Rails: Talk" group.
To post to this group, send email to
rubyonrails-talk-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
To unsubscribe from this group, send email to
rubyonrails-talk-unsubscribe-/JYPxA39Uh5TLH3MbocFFw@public.gmane.org
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---