README

Dynamo
======

Dynamo allows you to dynamically add attributes to an ActiveRecord model.  

Example
=======

Dynamo is a useful tool when there is the possibility you will need to change or add
attributes for a particular model.  This comes in handy when you have different customers
with different needs.

For example you might have a Contact model that normally has fields like:
first_name, last_name, and phone_number.  

This works fine for some of your customers, but now you have a customer who is asking to 
track age, and address too.

With dynamo you can just add those fields on the fly:
Contact.add_dynamo_field('age',:Number)
Contact.add_dynamo_field('address', :Text)

Now Contacts have these fields, and you didn't have to change your schema or do a migration.

Our application has a database per customer model so we are able to separate everything so
customer A's contacts have fields ('a', 'b', 'c')
customer B's contacts have fields ('x', 'y', 'z')

Otherwise we would have to have different models per customer, or cram all possible 
attributes in the model causing all customers to be overloaded with fields they don't care about.

If you want to then delete this dynamo attribute you can do:
Contact.remove_dynamo_field('age')

This will remove the field and all of its values!

Installation
============

./script/plugin install git@github.com:jacklin10/dynamo.git

Dynamo requires two tables so to generate a migration for those tables do:
./script/generate dynamo migration

Run the migration:
rake db:migrate

Details
=======

Dynamo works by creating two new tables.
dynamo_fields and dynamo_field_values

When you add a dynamo field it will save to dynamo_fields, and when you assign a value to the field
it will save in dynamo_field_values.

It was designed to read and write dynamo attributes the same way as normal static attributes so:
c = Contact.first
c.my_dynamo_field = 'xxx'
c.my_dynamo_field # xxx

works just as it would with a standard attribute.  

Contact.attributes will spill out the dynamo attributes and c.respond_to? :my_dynamo_field will return true.

Views:

Dynamo attributes will not automatically appear on your view pages however.  Not yet anyway.
I created a couple helpers you can use though ( see lib/dynamo_helper.rb)

Here's an example of the simple helper:
   <%= @supplier.dynamo_fields_p(f) %>

This will output all the dynamic field labels and a text field for its input encased
in <p> tags.

And here is a less pretty version that will blend in with any markup you are using:
<table width="50%">
	<%  @supplier.dynamo_fields do |field_name| %>
       <tr>
       	<td><%= field_name %>:</td>
			<td><%= f.text_field field_name %></td>
		</tr>
   <%  end %>
	<tr>
		<td>
			<%= f.submit %>
		</td>
	</tr>
</table>

Some other things I created within the application ( not inside dynamo) that might help you out:

If you want to display all the non dynamo attributes on the screen:

def dump_non_dynamo_attributes(model)
  # We don't want to display these because they aren't normally displayed/manipulated attributes.
  hide_these=['updated_at','creator_id','updater_id']
  returning [] do |show_these|
    # Need an instance so we have access to the instance methods
    dynamo_model_instance = model.new
    dynamo_model_instance.attributes.keys.each do |attr|
      if !dynamo_model_instance.is_dynamo_field?(attr) && !hide_these.include?(attr)
        show_these << attr        
      end
    end
  end
end

If you want to dump all the dynamo attributes:
def dump_dynamo_attributes(model)
  attrs=[]
  model.dynamo_fields.each do |attr|
    attrs << attr 
  end
  attrs
end

If you want to know which models in your application are using dynamo attributes you can do this:
ActiveRecord::Base.send(:subclasses).each do |model|
  @dynamo_models << model.name if model.instance_methods.include?('is_dynamo_field?')
end

Future
======

Right now the field types you can create are limited to Text, Number, and Decimal.
We would like to expand this to checkbox, select on, select many, etc.

We would also like the dynamo attributes to blend in more seamlessly with the view side of things so
you don't need to use any helpers just the normal rails helpers.

Performance needs improved a little also.  Need to make some more use of caching. 



Copyright (c) 2010 [name of plugin creator], released under the MIT license