Rails - Jan 2006 - Easy way to handle form input without a model class?

I have a couple forms that I''d like to be able to validate and
automatically populate, but it shouldn''t be based on AR.  In fact I
often have a bunch of small forms that I can''t really justify writing
a whole new model class for anyway.  I''d like to validate the form
input, and then use rails helpers to automatically populate the form
if validations fail.  I''ve already found some links on validating
without subclassing from AR, but nothing about auto populating forms
without a model, with or without rails helpers.

If there''s no existing way to do this, I already have an idea for
something simple.  I''d write a class that takes a hash at
initialization to populate instance variables and automatically add
accessors, and use method_missing to handle the object before it''s
initialized with the hash.  Pretty easy..but I just wanted to see if
something like this exists already.

Thanks,
Pat

Alright here''s what I came up with.  It''s a modification of
Peter
Donald''s ActiveForm
(http://www.realityforge.org/articles/2005/12/02/validations-for-non-activerecord-model-objects).
 The only real differences here are the initialize method, which sets
the attributes, and the method_missing, which returns the value of
instance_variable_get (which is nil if the instance variable doesn''t
exist).  Because it returns nil, the form helpers don''t complain about
a method not existing.

Hopefully some people can take a look at this and improve it a bit.  I
don''t really like how I''ve had to reimplement
method_missing..it does
the same exact thing as #[](key).  Also some of the stuff in
method_missing may be extraneous - I just hacked up a quick thing that
works for me.  I appreciate any comments, and big thanks to Peter
Donald for coming up with the original ActiveForm.



# Note ".valid?" method  must occur on object for validates_associated
class ActiveForm

  def initialize(init_values = {})
    init_values.each{ |key, value| instance_variable_set("@#{key}",
value) }
  end

  def [](key)
    instance_variable_get("@#{key}")
  end

  def method_missing( method_id, *args )
    if md = /_before_type_cast$/.match(method_id.to_s)
      attr_name = md.pre_match
      return self[attr_name] if self.respond_to?(attr_name)
    end

    instance_variable_get("@#{method_id.to_s}")
    #super
  end

protected
  def raise_not_implemented_error(*params)
    ValidatingModel.raise_not_implemented_error(*params)
  end

  def self.human_attribute_name(attribute_key_name)
    attribute_key_name.humanize
  end

  def new_record?
    true
  end

  # these methods must be defined before include
  alias save raise_not_implemented_error
  alias update_attribute raise_not_implemented_error

public
  include ActiveRecord::Validations

protected

  # the following methods must be defined after include so that they overide
  # methods previously included
  alias save! raise_not_implemented_error

  class << self
    def raise_not_implemented_error(*params)
      raise NotImplementedError
    end

    alias validates_uniqueness_of raise_not_implemented_error
    alias create! raise_not_implemented_error
    alias validate_on_create raise_not_implemented_error
    alias validate_on_update raise_not_implemented_error
    alias save_with_validation raise_not_implemented_error
  end
end

require ''dispatcher''
class Dispatcher
  class << self
    if ! method_defined?(:form_original_reset_application!)
      alias :form_original_reset_application! :reset_application!
      def reset_application!
        form_original_reset_application!
        Dependencies.remove_subclasses_for(ActiveForm) if defined?(ActiveForm)
      end
    end
  end
end


On 1/19/06, Pat Maddox <pergesu@gmail.com> wrote:
> I have a couple forms that I''d like to be able to validate and
> automatically populate, but it shouldn''t be based on AR.  In fact
I
> often have a bunch of small forms that I can''t really justify
writing
> a whole new model class for anyway.  I''d like to validate the form
> input, and then use rails helpers to automatically populate the form
> if validations fail.  I''ve already found some links on validating
> without subclassing from AR, but nothing about auto populating forms
> without a model, with or without rails helpers.
>
> If there''s no existing way to do this, I already have an idea for
> something simple.  I''d write a class that takes a hash at
> initialization to populate instance variables and automatically add
> accessors, and use method_missing to handle the object before it''s
> initialized with the hash.  Pretty easy..but I just wanted to see if
> something like this exists already.
>
> Thanks,
> Pat
>

See this page:

http://rails.techno-weenie.net/tip/2005/11/19/validate_your_forms_with_a
_table_less_model

It''s awesome and if you know how to tweak it, you can make it do some
other cool things as well.


-----Original Message-----
From: rails-bounces@lists.rubyonrails.org
[mailto:rails-bounces@lists.rubyonrails.org] On Behalf Of Pat Maddox
Sent: Thursday, January 19, 2006 1:59 AM
To: rails@lists.rubyonrails.org
Subject: [Rails] Re: Easy way to handle form input without a model
class?


Alright here''s what I came up with.  It''s a modification of
Peter
Donald''s ActiveForm
(http://www.realityforge.org/articles/2005/12/02/validations-for-non-act
iverecord-model-objects).
 The only real differences here are the initialize method, which sets
the attributes, and the method_missing, which returns the value of
instance_variable_get (which is nil if the instance variable doesn''t
exist).  Because it returns nil, the form helpers don''t complain about
a
method not existing.

Hopefully some people can take a look at this and improve it a bit.  I
don''t really like how I''ve had to reimplement
method_missing..it does
the same exact thing as #[](key).  Also some of the stuff in
method_missing may be extraneous - I just hacked up a quick thing that
works for me.  I appreciate any comments, and big thanks to Peter Donald
for coming up with the original ActiveForm.



# Note ".valid?" method  must occur on object for validates_associated
class ActiveForm

  def initialize(init_values = {})
    init_values.each{ |key, value| instance_variable_set("@#{key}",
value) }
  end

  def [](key)
    instance_variable_get("@#{key}")
  end

  def method_missing( method_id, *args )
    if md = /_before_type_cast$/.match(method_id.to_s)
      attr_name = md.pre_match
      return self[attr_name] if self.respond_to?(attr_name)
    end

    instance_variable_get("@#{method_id.to_s}")
    #super
  end

protected
  def raise_not_implemented_error(*params)
    ValidatingModel.raise_not_implemented_error(*params)
  end

  def self.human_attribute_name(attribute_key_name)
    attribute_key_name.humanize
  end

  def new_record?
    true
  end

  # these methods must be defined before include
  alias save raise_not_implemented_error
  alias update_attribute raise_not_implemented_error

public
  include ActiveRecord::Validations

protected

  # the following methods must be defined after include so that they
overide
  # methods previously included
  alias save! raise_not_implemented_error

  class << self
    def raise_not_implemented_error(*params)
      raise NotImplementedError
    end

    alias validates_uniqueness_of raise_not_implemented_error
    alias create! raise_not_implemented_error
    alias validate_on_create raise_not_implemented_error
    alias validate_on_update raise_not_implemented_error
    alias save_with_validation raise_not_implemented_error
  end
end

require ''dispatcher''
class Dispatcher
  class << self
    if ! method_defined?(:form_original_reset_application!)
      alias :form_original_reset_application! :reset_application!
      def reset_application!
        form_original_reset_application!
        Dependencies.remove_subclasses_for(ActiveForm) if
defined?(ActiveForm)
      end
    end
  end
end


On 1/19/06, Pat Maddox <pergesu@gmail.com> wrote:
> I have a couple forms that I''d like to be able to validate and 
> automatically populate, but it shouldn''t be based on AR.  In fact
I
> often have a bunch of small forms that I can''t really justify
writing
> a whole new model class for anyway.  I''d like to validate the form
> input, and then use rails helpers to automatically populate the form 
> if validations fail.  I''ve already found some links on validating 
> without subclassing from AR, but nothing about auto populating forms 
> without a model, with or without rails helpers.
>
> If there''s no existing way to do this, I already have an idea for 
> something simple.  I''d write a class that takes a hash at 
> initialization to populate instance variables and automatically add 
> accessors, and use method_missing to handle the object before it''s
> initialized with the hash.  Pretty easy..but I just wanted to see if 
> something like this exists already.
>
> Thanks,
> Pat
>
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