Rails - Mar 2009 - MonkeyPatching ActiveRecord::Base class

I am trying to monkey-patch the ActiveRecord::Base class to incorporate
a generic search class method so that it can be used by all model
classes which need this functionality.  Since model classes directly
inherit from ActiveRecord::Base and unlike controllers and helpers, do
not have an ancestor class defined, I think I am forced to open the
ActiveRecord::Base class and patch it?  May be I am wrong.  Anyway, here
is my code in the active_record_extensions.rb file that I created in the
RAILS_ROOT/lib directory:

module ActiveRecord

  class Base
    def self.search(search, current_page)
      if search.blank?
        paginate(:all, :page => current_page || 1, :per_page => 5)
      else
        paginate(:all, :conditions => ["name LIKE ?",
"%#{search}%"],
:order => ''name'',
          :page => current_page || 1, :per_page => 5)
      end
    end
  end

end

Note that paginate method comes from the will_paginate plugin installed
in vendor/plugins directory.

This does not work.  My program is having trouble with the paginate
method from will_paginate plugin being called in the code shown above?

This seems to be a load_path issue?  One way to solve this is to install
will_paginate as a gem and then require it before calling paginate?  But
is there a way to make with work as a plugin as I have it currently for
creating this generic routine?

Thanks for your time in advance.

Bharat
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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 Mar 23, 2009, at 5:09 PM, Bharat Ruparel wrote:
>
> I am trying to monkey-patch the ActiveRecord::Base class to  
> incorporate
> a generic search class method so that it can be used by all model
> classes which need this functionality.  Since model classes directly
> inherit from ActiveRecord::Base and unlike controllers and helpers, do
> not have an ancestor class defined, I think I am forced to open the
> ActiveRecord::Base class and patch it?  May be I am wrong.  Anyway,  
> here
Why not create your method as a module and then include it into the  
classes you need it?  Look at any of the plugins out there that are of  
the "acts_as_xxxx" variety which add methods to the model they are  
called from... just follow those examples and you shouldn''t need to  
directly modify AR::Base like this.

> is my code in the active_record_extensions.rb file that I created in  
> the
> RAILS_ROOT/lib directory:
>
> module ActiveRecord
>
>  class Base
>    def self.search(search, current_page)
>      if search.blank?
>        paginate(:all, :page => current_page || 1, :per_page => 5)
>      else
>        paginate(:all, :conditions => ["name LIKE ?",
"%#{search}%"],
> :order => ''name'',
>          :page => current_page || 1, :per_page => 5)
>      end
>    end
>  end
>
> end
>
> Note that paginate method comes from the will_paginate plugin  
> installed
> in vendor/plugins directory.
>
> This does not work.  My program is having trouble with the paginate
> method from will_paginate plugin being called in the code shown above?
>
> This seems to be a load_path issue?  One way to solve this is to  
> install
> will_paginate as a gem and then require it before calling paginate?   
> But
> is there a way to make with work as a plugin as I have it currently  
> for
> creating this generic routine?
>
> Thanks for your time in advance.
>
> Bharat
> -- 
> Posted via http://www.ruby-forum.com/.
>
> >

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Thanks Phillip.  I will follow your advice and see if I can do it.
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

> Why not create your method as a module and then include it into the  
> classes you need it?  Look at any of the plugins out there that are of  
> the "acts_as_xxxx" variety which add methods to the model they
are
> called from... just follow those examples and you shouldn''t need
to
> directly modify AR::Base like this.
Further, adding a method to a class is a perfectly reasonable solution, and is 
not "monkey patching". That''s when you change a preexisting
method, simply
because it offered no hook for you to override.

In order from sublime to icky...

  - delegate to the behavior you need
  - include/extend the behavior
  - inherit the behavior
  - add the behavior to your base class
  - trigger the behavior with an ''if'' statement
  - monkey-patch the behavior into a closed class

Yes, folks, the lowly ''if'' statement is the second-worst
option in Object
Oriented programming. Use it with extreme caution!


--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

Could not get to it yesterday due to other work.  Am still struggling 
with it.  There is something basic that I do not understand.  I have 
looked at acts_as plugins (list and tree for instance).  I am afraid 
that is not going to help me.  Here is the thing that I do not get:

1.  The Rails lib directory contains reusable code that can be used 
anywhere in that particular Rails application.  Following that basic 
concept, I created a file called active_records_extensions.rb in it 
which has the following slightly modified code from the previous 
posting:

module ActiveRecord

  class Base

    class << self

      def search(search, current_page)
        if search.blank?
          WillPaginate::Finder::paginate(:all, :page => current_page || 
1, :per_page => 5)
        else
          WillPaginate::Finder::paginate(:all, :conditions => ["name 
LIKE ?", "%#{search}%"], :order => ''name'',
            :page => current_page || 1, :per_page => 5)
        end
      end
    end

  end

end

Now search is supposed to be a class method since it is called from the 
index method of a controller like this:

  def index
    @pizzas = Pizza.search(params[:search], params[:page])
  end

That is why I am defining the search method as a class method for 
ActiveRecord::Base class as shown above.  I have done this sort of thing 
many times before without any problems.  The twist this time is that the 
"Search" method is calling the paginate class method of will_paginate 
plugin.

First, I tried requiring the will_paginate class method, but that did 
not work.  Next, I tried giving the full path for the paginate class 
method as shown above in the code.  Still, I get the same error.  Here 
is the stack trace snippet.

NoMethodError (undefined method `search'' for
#<Class:0xb7143b6c>):
   
/usr/local/lib/ruby/gems/1.8/gems/activerecord-2.1.2/lib/active_record/base.rb:1672:in
`method_missing_without_paginate''
    /vendor/plugins/will_paginate/lib/will_paginate/finder.rb:170:in 
`method_missing''
    /app/controllers/pizzas_controller.rb:17:in `index''
   
/usr/local/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/base.rb:1166:in
`send''
   
/usr/local/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/base.rb:1166:in
`perform_action_without_filters''
   
/usr/local/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/filters.rb:579:in
`call_filters''
   
/usr/local/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/filters.rb:572:in
`perform_action_without_benchmark''
   
/usr/local/lib/ruby/gems/1.8/gems/actionpack-2.1.2/lib/action_controller/benchmarking.rb:68:in
`perform_action_without_rescue''
    /usr/local/lib/ruby/1.8/benchmark.rb:293:in `measure''

I am hoping someone can help me understand what is it that I am missing. 
I am doing this project to further my knowledge about designing reusable 
code in Rails and there is something fundamental that I am not able to 
grasp.

As always, thanks for your time.

Bharat
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

I  have reduced the problem down to the following:  whatever method I 
define in the lib directory under active_record_extensions.rb, is not 
being loaded by rails.  This has worked perfectly for me in a large 
Rails 2.1.0 application.  So here is the problem:

RAILS_ROOT/lib/active_record_extensions.rb:

module ActiveRecord

  class Base

    class << self

      def hello
        puts "Hello from active record"
      end

    end

  end

end

I start the server.  I load Rails Console and try to invoke hello method 
on any model class.  I get exactly the same error as shown below on 
Pizza class for example:

bruparel@bcr-d810:~/exp/pizzeria-3$ ruby ./script/console
Loading development environment (Rails 2.1.2)
>> Pizza.hello
NoMethodError: undefined method `hello'' for #<Class:0xb784607c>
  from 
/usr/local/lib/ruby/gems/1.8/gems/activerecord-2.1.2/lib/active_record/base.rb:1672:in
`method_missing_without_paginate''
  from 
/home/bruparel/exp/pizzeria-3/vendor/plugins/will_paginate/lib/will_paginate/finder.rb:170:in
`method_missing''
  from (irb):1
>> CrustType.hello
NoMethodError: undefined method `hello'' for #<Class:0xb72087dc>
  from 
/usr/local/lib/ruby/gems/1.8/gems/activerecord-2.1.2/lib/active_record/base.rb:1672:in
`method_missing_without_paginate''
  from 
/home/bruparel/exp/pizzeria-3/vendor/plugins/will_paginate/lib/will_paginate/finder.rb:170:in
`method_missing''
  from (irb):2

Does anyone know what is going on?
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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 Mar 25, 3:04 pm, Bharat Ruparel
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> Does anyone know what is going on?
That file''s not going to magically load itself. you need to require it
(eg from an initializer in config/initializers)
> --
> Posted viahttp://www.ruby-forum.com/.
--~--~---------~--~----~------------~-------~--~----~
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@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

On Wed, Mar 25, 2009 at 10:04 AM, Bharat Ruparel
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
>
> I  have reduced the problem down to the following:  whatever method I
> define in the lib directory under active_record_extensions.rb, is not
> being loaded by rails.
I found the same problem when upgrading an app to 2.3.2 yesterday.  I
fixed it using

Dir.glob( "#{ RAILS_ROOT }/lib/*.rb" ).each { |f| require f }

in config/environment.rb.



-- 
Greg Donald
http://destiney.com/

--~--~---------~--~----~------------~-------~--~----~
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@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

Thank you Fred and Greg.  You both are right.  I had a similar load 
configuration block as Greg shows here in my environment file in the 
application where it worked fine and had forgotten all about it.  For 
this little application, I put the following statement at the end of 
config/environment.rb:

  require "#{RAILS_ROOT}/lib/active_record_extensions.rb"

And everything works fine.  I was under the impression that everything 
in the lib directory gets loaded automatically which is apparently an 
incorrect assumption.

Question is: what is the significance of the "lib" directory then in a
Rails environment?  If it just gets added in the Rails load path and 
nothing else then it leaves me scratching my head.  Either don''t put in
the load path automatcially or if we do then load whatever is in there 
automatically too.  Don''t you think Rails is at odds with itself here?

Bharat
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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 25 Mar 2009, at 16:11, Bharat Ruparel wrote:
>
> Question is: what is the significance of the "lib" directory then
in a
> Rails environment?  If it just gets added in the Rails load path and
> nothing else then it leaves me scratching my head.  Either don''t
put
> in
> the load path automatcially or if we do then load whatever is in there
> automatically too.  Don''t you think Rails is at odds with itself
here?
>
Except for the production mode stuff, nothing gets loaded  
automatically (the const_missing hook can make it seem that way  
though. The difference with a file like the one you had is that there  
isn''t a top level constant one would naturally refer to)

Fred
> Bharat
> -- 
> Posted via http://www.ruby-forum.com/.
>
> >

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---

"The difference with a file like the one you had is that there
isn''t a top level constant one would naturally refer to)"

Thanks for the explanation Fred.  But I don''t understand this.  Can you
give me a simple example?

Bharat
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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 Mar 25, 8:22 pm, Bharat Ruparel
<rails-mailing-l...-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:
> "The difference with a file like the one you had is that there
> isn''t a top level constant one would naturally refer to)"
>
> Thanks for the explanation Fred.  But I don''t understand this.
 Can you
> give me a simple example?
>
If what you were doing was providing a class that other bits of your
app use then you might have discombobulator.rb which defined
Discombobulator, and bits of your app might do
Discombobulator.discombobulate. When they did that and if the file had
not been loaded yet then this would trigger const_missing (since there
is no Discombobulator constant). Rails'' response to this is to search
for a file called discombobulator.rb and try and load it.

However when you have a file in lib that is just adding a method to
some existing class or overriding something then there is no constant
like Discombobulator that will trigger loading of the file.

Fred
--~--~---------~--~----~------------~-------~--~----~
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@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/rubyonrails-talk?hl=en
-~----------~----~----~----~------~----~------~--~---

"However when you have a file in lib that is just adding a method to
some existing class or overriding something then there is no constant
like Discombobulator that will trigger loading of the file."

Got it.  Thanks.
-- 
Posted via http://www.ruby-forum.com/.

--~--~---------~--~----~------------~-------~--~----~
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
-~----------~----~----~----~------~----~------~--~---