duck_chain¶ ↑

This gem’s purpose is to generate basic chainable search methods on models in Rails 3 similar to searchlogic’s dynamic named scopes.

duck_chain’s original purpose is to help with the transition from Rails 2 to 3. A lot of projects use searchlogic, and while metasearch is a fine replacement, it doesn’t provide the dynamic named scopes (ie Post.title_equals(“foobar”).content_like(“I like pie”). To help with the transition, duck_chain extends ActiveRecord and creates extra chainable model methods for attributes you specifiy which act similar to the basic searchlogic named scopes. The methods simply return Arel where cluases so you can chain them with other methods.

Only the basic single table methods are supported (eq, not_equal, gte, like, etc.). Meaning you can’t do Post.post_comments_title_eq(“This blog sux”). Legacy code like that should be converted into an Arel where method, metasearch search method, or whatever you decide to go with for Rails 3. Again, the gem was built to help with the transition and provide some of the basic search methods people using searchlogic are used to in Rails 3. Plus, I personally like typing out Post.created_at_gte(Time.now).content_like(“I like shorts. They’re comfortable and easy to wear.”) more than Post.where([‘created_at >= ?’, Time.now]).where(“content LIKE ‘%I like shorts. They’re comfortable and easy to wear.%‘”). Just seems a little clearer this way. :)

Include the gem in your GemFile like any other gem.

Consider the following model…

class Post < ActiveRecord::Base
  # Fields:
  #   id:integer
  #   title:string
  #   content:text
  #   url:string
  #   comment_counter:integer
  #   created_at:datetime
  #   updated_at:datetime
end

To have duck_chain bind to the title, content, and url attributes of the model…

class Post < ActiveRecord::Base
  duck_chain :content, 'title', :url
  # Note you can use symbols or strings in your list of attributes
end

Calling duck_chain creates a bunch of chainable methods for the Post model for the content, title, and url attributes

Or, instead of specifying exactly which attributes to chain, you can call

class Post < ActiveRecord::Base
  duck_chain_all
end

which will add duck_chain to all of the attributes of the model …

Example new methods related to the title attribute:

The following ‘eq’ methods can accept a string, array, or range

• title_eq

• title_equals

• title_is

• title_in

• title_neq

• title_not_equal

• title_is_not

• title_does_not_equal

• title_not_in

The following ‘like’ methods should only be passed a string

• title_like

• title_begins_with

• title_ends_with

• title_not_like

• title_not_begin_with

• title_not_end_with

The following ‘range’ methods should only be passed a string

• title_gt

• title_greater_than

• title_gte

• title_greater_than_or_equal_to

• title_lt

• title_less_than

• title_lte

• title_less_than_or_equal_to

Then, you can just use the methods in your code like you did with searchlogic… Post.title_eq(“Foobar”).where(…).content_like(“Blah”)

There might be some cases where you’d rather just only bind the ‘eq’ methods to an attribute rather than all of them…

class Post < ActiveRecord::Base
  # Will only create the _eq, _is, _neq, _in, etc. methods
  duck_chain_eq :content, 'title', :url
end

You can also create only the ‘like’ and ‘range’ methods in a similar fasion…

class Post < ActiveRecord::Base
  duck_chain_like :content
  duck_chain_range :created_at
end