Rails - Sep 2005 - common code for models?

It looks to me as if controllers/application.rb is only accessible
from controllers and helpers/*.rb is only accessible from templates.
So, neither one is accessible from a model.  Am I missing something?

Basically, I want to know where to put methods that can be used by
any of several models and what I need to do to access them.  It has
been suggested that I put the methods into files in lib/, but I''m
not sure how to access them (from there) in my model code.

-r
-- 
email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
http://www.cfcl.com        - Canta Forda Computer Laboratory
http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.

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On Sep 19, 2005, at 3:42 PM, Rich Morin wrote:
> Basically, I want to know where to put methods that can be used by
> any of several models and what I need to do to access them.  It has
> been suggested that I put the methods into files in lib/, but I''m
> not sure how to access them (from there) in my model code.
app/models/common_behavior.rb
   module CommonBehavior
     def foobar; end
   end

app/models/some_model.rb
   require_dependency ''common_behavior''
   class SomeModel < ActiveRecord::Base
     include CommonBehavior
   end

app/models/another_model.rb
   require_dependency ''common_behavior''
   class AnotherModel < ActiveRecord::Base
     include CommonBehavior
   end

Now both classes have the foobar instance method.

Note that I put everything modeling my domain in the models dir,
not just persistence classes.

Regards,
jeremy
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OK, I got pointed to

   http://wiki.rubyonrails.com/rails/show/ExtendingActiveRecordExample
   http://wiki.rubyonrails.com/rails/show/UnderstandingWhatMethodsGoesWhere

which appear to address this general problem.  Now I''m hassling with
the specifics (sigh).

-r
-- 
email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
http://www.cfcl.com        - Canta Forda Computer Laboratory
http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.

On 9/19/05, Rich Morin <rdm-go8te9J4rpw@public.gmane.org>
wrote:
> It looks to me as if controllers/application.rb is only accessible
> from controllers and helpers/*.rb is only accessible from templates.
> So, neither one is accessible from a model.  Am I missing something?
> 
> Basically, I want to know where to put methods that can be used by
> any of several models and what I need to do to access them.  It has
> been suggested that I put the methods into files in lib/, but I''m
> not sure how to access them (from there) in my model code.
This can be done through a mixin (which is what a helper is basically..)

# lib/my_module_mixin.rb
module MyModelMixin
  def xoo
    ''xoo is new''
  end
end

# app/models/foo.rb
class Foo < ActiveRecord::Base
  include MyModelMixin
end

# usage
@foo.zoo
# => ''xoo is new''

Now, let''s say you want to add a class method:

# lib/my_module_mixin.rb
module MyModelMixin
  def self.included(base)
    base.extend(ClassMethods)
  end

  def xoo
    ''xoo is new''
  end

  module ClassMethods
    def bar
      ''bar''
    end
  end
end


# usage
Foo.bar
# => ''bar''

Still missing something.  I have the following code in place:


lib/edge_list.rb
----------------

module Edge_list

   # self.neighbors - find neighbors for a file_node, etc.

   def self.neighbors
     ...
   end
end


models/file_node.rb
-------------------

class FileNode < ActiveRecord::Base

   require ''edge_list''
   include Edge_list

   # This should probably be somewhere else...

   def self.neighbors_x
     ...
   end
end


views/admin/show.rhtml
----------------------

...
<% for edge in FileNode.neighbors %>
<%=	sprintf("%d -(%d)-> %d\n",
		edge.src_id, edge.edge_desc_id, edge.dst_id)
%>
<% end %>
...


If I try the code in this form, it gets a nastygram:

   undefined method `neighbors'' for FileNode:Class

If I change "for edge in FileNode.neighbors" to
             "for edge in FileNode.neighbors_x" in
views/admin/show.rhtml,
it works just fine.  Wazzup?

-r
-- 
email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
http://www.cfcl.com        - Canta Forda Computer Laboratory
http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.

OK, I tried Jeremy Kemper''s suggestion, but it''s still failing
for me.
Is there some magic that''s needed to get show.rhtml to "see"
methods
which have been include''d into file_node.rb?  Here''s what I
have now:

models/edge_list.rb
------------------

module EdgeList

   # self.neighbors - find neighbors for a file_node, etc.

   def self.neighbors
     ...
   end
end


models/file_node.rb
-------------------

require_dependency ''edge_list''

class FileNode < ActiveRecord::Base

   include EdgeList

   # This should probably be somewhere else...

   def self.neighbors_x
     ...
   end
end


views/admin/show.rhtml
----------------------

...
<% for edge in FileNode.neighbors %>
<%=	sprintf("%d -(%d)-> %d\n",
		edge.src_id, edge.edge_desc_id, edge.dst_id)
%>
<% end %>
...
-- 
email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
http://www.cfcl.com        - Canta Forda Computer Laboratory
http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.

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On Sep 19, 2005, at 4:37 PM, Rich Morin wrote:
> OK, I tried Jeremy Kemper''s suggestion, but it''s still
failing for me.
> Is there some magic that''s needed to get show.rhtml to
"see" methods
> which have been include''d into file_node.rb?  Here''s what
I have now:
module SomeModule
   def self.a_class_method; end
   def an_instance_method; end
end

class Foo
   include SomeModule
end

This includes the *instance methods* defined in SomeModule in Foo.
a_class_method is a method of the SomeModule module itself and is
not pulled into Foo.

Here''s a common idiom for including both instance and class methods:

module SomeModule
   # When you do "class Foo; include SomeModule; end"
   # Ruby calls SomeModule.included(Foo) if it''s defined.
   def self.included(base_class)
     # Call super to get the normal behavior of pulling in the
     # instance methods.
     super

     # Now extend the class itself with our class methods.
     base_class.extend ClassMethods
   end

   module ClassMethods
     def a_class_method
       # ...
     end
   end

   def an_instance_method
   end
end

Now "class Foo; include SomeModule; end" pulls in both class and
instance methods:  Foo.a_class_method, Foo.new.an_instance_method.

For further study, check out the Pickaxe book.  This is more Ruby
than Rails territory.

jeremy
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On 9/19/05, Rich Morin <rdm-go8te9J4rpw@public.gmane.org>
wrote:
> 
> OK, I tried Jeremy Kemper''s suggestion, but it''s still
failing for me.
> Is there some magic that''s needed to get show.rhtml to
"see" methods
> which have been include''d into file_node.rb? Here''s what
I have now:

<snip/>

Try this:

In conig/environment.rb:

require ''edge_list''
ActiveRecord::Base.class_eval do
include Edge_list
end

Josh


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Following Jeremy Kemper''s advice, I read up a bit on class and instance
methods (using Rails to learn Ruby is not without peril :-).  It turns
out that I didn''t really NEED a class method, so I was able to simplify
things quite a bit.

-r
-- 
email: rdm-go8te9J4rpw@public.gmane.org; phone: +1 650-873-7841
http://www.cfcl.com        - Canta Forda Computer Laboratory
http://www.cfcl.com/Meta   - The FreeBSD Browser, Meta Project, etc.