Rails - Mar 2005 - Helpers in Rails

Ok, so, I have a method that I need to use in several models and two
controllers.  I don''t want to duplicate code, and initially,
rail''s
concept of a helper seemed like a good fit, but it looks like maybe it
only works with controllers, so maybe not.  I''m a pretty much a nuby,
but I think maybe I want to do a mixin?  If so, where would the module
with my method go within the rails application folder structure?  And
how do I do a mixin?
-- 
Bob Aman

On Tue, 29 Mar 2005 19:42:22 -0500, Bob Aman
<vacindak-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:
> Ok, so, I have a method that I need to use in several models and two
> controllers.  I don''t want to duplicate code, and initially,
rail''s
> concept of a helper seemed like a good fit, but it looks like maybe it
> only works with controllers, so maybe not.  I''m a pretty much a
nuby,
> but I think maybe I want to do a mixin?  If so, where would the module
> with my method go within the rails application folder structure?  And
> how do I do a mixin?
> --
> Bob Aman
Hi Bob

I would suggest creating a module in the ''lib'' directory.  For
example, you create a file "testmodule.rb" in the lib directory.  In
your model file, you would do:

require_dependency "testmodule"

class MyModule < ActiveRecord::Base
  include TestModule 

  ...
end

Hope that helps,
Dave

-- 
Dave Goodlad
dgoodlad-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org or
dave-eHfbeeWWzZOw5LPnMra/2Q@public.gmane.org
http://david.goodlad.ca/

> Hi Bob
> 
> I would suggest creating a module in the ''lib'' directory.
For
> example, you create a file "testmodule.rb" in the lib directory. 
In
> your model file, you would do:
> 
> require_dependency "testmodule"
> 
> class MyModule < ActiveRecord::Base
>   include TestModule
> 
>   ...
> end
> 
> Hope that helps,
> Dave
Hmm, ok, what if the method being mixed in is a class method?  It
seems to give me a method missing exception.
-- 
Bob Aman

On Tuesday 29 March 2005 22:51, Bob Aman wrote:
> Hmm, ok, what if the method being mixed in is a class method?  It
> seems to give me a method missing exception.
A module''s methods can be added to a class using SomeClass.extend. For
example

module ValidationsLayer
  def field(name, *args={})
    options = args.last.kind_of?(Hash) ? args.pop : {}
    args.each {|name| options[name] = true}
    
    validates_uniqueness_of(name, :allow_nil => true) if options[:unique]
    validates_numericality_of(name, :allow_nil => true) if options[:number]
    validates_length_of(name, options[:length].merge(:allow_nil => true)) \
      if options[:length]
    validates_associated(name, :allow_nil => true) if options[:validate]
    validates_presence_of(name) if options[:required]
  end
  def at_least(n)
    {:minimum => n}
  end
  def at_most(n)
    {:maximum => n}
  end
  def exactly(n)
    {:is => n}
  end
  def within(a, b=nil)
    a = (a..b) if b
    {:within => a}
  end
end

class User
  extend ValidationsLayer

  field :login, :required, :unique, :length => at_most(64)
  field :email, :required, :unique, :length => within(8..255)
  field :age, :required, :number
end

-- 

Nicholas Seckar aka. Ulysses

> A module''s methods can be added to a class using SomeClass.extend.
For example
What if I have both class and instance methods in my module?

-- 
Bob Aman

On Wednesday 30 March 2005 00:11, Bob Aman wrote:
> What if I have both class and instance methods in my module?
As was documented in another thread, you will often see this snipped in Rails 
code:

module SomeModule
  def append_features(base) # this is called when a class include''s a
module
    super(base) # do the typical behavior,
    base.extend(ClassMethods) # automatically extend the classmethods
  end
  
  module ClassMethods
    def some_class_method
    end
  end

  def some_instance_method
  end
end

In a future release, modules will automatically perform the extend if 
ClassMethods is present. So, the code then will be

module SomeModule
  instance methods here
  module ClassMethods
    ...
  end
end

-- 

Nicholas Seckar aka. Ulysses