Ransack

Ransack is a rewrite of MetaSearch created by Ernie Miller and maintained by Ryan Bigg, Jon Atack and a great group of contributors. While it supports many of the same features as MetaSearch, its underlying implementation differs greatly from MetaSearch, and backwards compatibility is not a design goal.

Ransack enables the creation of both simple and advanced search forms against your application's models (demo source code here). If you're looking for something that simplifies query generation at the model or controller layer, you're probably not looking for Ransack (or MetaSearch, for that matter). Try Squeel instead.

Getting started

Ransack is currently compatible with Rails 3.x, 4.0, 4.1 and 4.2.

In your Gemfile, for the last officially released Ransack gem:

gem 'ransack'

Or, if you would like to use the latest updates:

gem 'ransack', github: 'activerecord-hackery/ransack'

The other branches (rails-4, rails-4.1, and rails-4.2) were each used for developing and running Ransack with the latest upcoming version of Rails at the time. They are lighter and somewhat faster-running because they do not have to support previous versions of Rails and Active Record. Once support for that Rails version is merged from the branch into Ransack master, the branch is no longer actively maintained -- unless the open source community submits pull requests to maintain them. You are welcome to do so!

Usage

Ransack can be used in one of two modes, simple or advanced.

Simple Mode

This mode works much like MetaSearch, for those of you who are familiar with it, and requires very little setup effort.

If you're coming from MetaSearch, things to note:

The default param key for search params is now :q, instead of :search. This is primarily to shorten query strings, though advanced queries (below) will still run afoul of URL length limits in most browsers and require a switch to HTTP POST requests. This key is configurable.
form_for is now search_form_for, and validates that a Ransack::Search object is passed to it.
Common ActiveRecord::Relation methods are no longer delegated by the search object. Instead, you will get your search results (an ActiveRecord::Relation in the case of the ActiveRecord adapter) via a call to Search#result.
If passed distinct: true, result will generate a SELECT DISTINCT to avoid returning duplicate rows, even if conditions on a join would otherwise result in some.

Please note that for many databases, a sort on an associated table's columns may result in invalid SQL with distinct: true -- in those cases, you're on your own, and will need to modify the result as needed to allow these queries to work. If distinct: true is causing you problems, another way to remove duplicates is to call #to_a.uniq on your collection instead (see the next section below).

In your controller

def index
  @q = Person.search(params[:q])
  @people = @q.result(distinct: true)
end

or without distinct:true, for sorting on an associated table's columns (in this example, with preloading each Person's Articles and pagination):

def index
  @q = Person.search(params[:q])
  @people = @q.result.includes(:articles).page(params[:page])
  # or use `to_a.uniq` to remove duplicates (can also be done in the view):
  @people = @q.result.includes(:articles).page(params[:page]).to_a.uniq
end

In your view

The two primary Ransack view helpers are search_form_for and sort_link, which are defined in Ransack::Helpers::FormHelper.

1. Ransack's `search_form_for` helper replaces `form_for` for creating the view search form:

<%= search_form_for @q do |f| %>

  # Search if the name field contains...
  <%= f.label :name_cont %>
  <%= f.search_field :name_cont %>

  # Search if an associated articles.title starts with...
  <%= f.label :articles_title_start %>
  <%= f.search_field :articles_title_start %>

  # Attributes may be chained. Search multiple attributes for one value...
  <%= f.label :name_or_description_or_email_or_articles_title_cont %>
  <%= f.search_field :name_or_description_or_email_or_articles_title_cont %>

  <%= f.submit %>
<% end %>

cont (contains) and start (starts with) are just two of the available search predicates. See Constants for a full list and the wiki for more information.

The search_form_for answer format can be set like this:

<%= search_form_for(@q, format: :pdf) do |f| %>

<%= search_form_for(@q, format: :json) do |f| %>

2. Ransack's `sort_link` helper creates table headers that are sortable links:

<%= content_tag :th, sort_link(@q, :name) %>

Additional options can be passed after the column attribute, like a different column title or a default sort order:

<%= content_tag :th, sort_link(@q, :name, 'Last Name', default_order: :desc) %>

Advanced Mode

"Advanced" searches (ab)use Rails' nested attributes functionality in order to generate complex queries with nested AND/OR groupings, etc. This takes a bit more work but can generate some pretty cool search interfaces that put a lot of power in the hands of your users. A notable drawback with these searches is that the increased size of the parameter string will typically force you to use the HTTP POST method instead of GET. :(

This means you'll need to tweak your routes...

resources :people do
  collection do
    match 'search' => 'people#search', via: [:get, :post], as: :search
  end
end

... and add another controller action ...

def search
  index
  render :index
end

... and update your search_form_for line in the view ...

<%= search_form_for @q, url: search_people_path,
                        html: { method: :post } do |f| %>

Once you've done so, you can make use of the helpers in Ransack::Helpers::FormBuilder to construct much more complex search forms, such as the one on the demo page (source code here).

Ransack #search method

Ransack will try to to make #search available in your models, but in the case that #search has already been defined, you can use #ransack instead. For example the following would be equivalent:

Article.search(params[:q])
Article.ransack(params[:q])

Associations

You can easily use Ransack to search for objects in has_many and belongs_to associations.

Given you have these associations ...

class Employee < ActiveRecord::Base
  belongs_to :supervisor

  # has attributes first_name:string and last_name:string
end

class Department < ActiveRecord::Base
  has_many :supervisors

  # has attribute title:string
end

class Supervisor < ActiveRecord::Base
  belongs_to :department
  has_many :employees

  # has attribute last_name:string
end

... and a controller ...

class SupervisorsController < ApplicationController
  def index
    @q = Supervisor.search(params[:q])
    @supervisors = @q.result.includes(:department, :employees)
  end
end

... you might set up your form like this ...

<%= search_form_for @q do |f| %>
  <%= f.label :last_name_cont %>
  <%= f.search_field :last_name_cont %>

  <%= f.label :department_title_cont %>
  <%= f.search_field :department_title_cont %>

  <%= f.label :employees_first_name_or_employees_last_name_cont %>
  <%= f.search_field :employees_first_name_or_employees_last_name_cont %>

  <%= f.submit "search" %>
<% end %>
...
<%= content_tag :table %>
  <%= content_tag :th, sort_link(@q, :last_name) %>
  <%= content_tag :th, sort_link(@q, 'departments.title') %>
  <%= content_tag :th, sort_link(@q, 'employees.last_name') %>
<% end %>

Using Ransackers to add custom search functions via Arel

The main premise behind Ransack is to provide access to Arel predicate methods. Ransack provides special methods, called ransackers, for creating additional search functions via Arel. More information about ransacker methods can be found here in the wiki. Feel free to contribute working ransacker code examples to the wiki!

Authorization (whitelisting/blacklisting)

By default, searching and sorting are authorized on any column of your model and no class methods/scopes are whitelisted.

Ransack adds four methods to ActiveRecord::Base that you can redefine as class methods in your models to apply selective authorization: ransackable_attributes, ransackable_associations, ransackable_scopes and ransortable_attributes.

Here is how these four methods are implemented in Ransack:

def ransackable_attributes(auth_object = nil)
  # By default returns all column names and any defined ransackers as an array
  # of strings. For overriding with a whitelist array of strings.
  column_names + _ransackers.keys
end

def ransackable_associations(auth_object = nil)
  # By default returns the names of all associations as an array of strings.
  # For overriding with a whitelist array of strings.
  reflect_on_all_associations.map { |a| a.name.to_s }
end

def ransortable_attributes(auth_object = nil)
  # By default returns the names of all attributes for sorting as an array of
  # strings. For overriding with a whitelist array of strings.
  ransackable_attributes(auth_object)
end

def ransackable_scopes(auth_object = nil)
  # By default returns an empty array, i.e. no class methods/scopes
  # are authorized. For overriding with a whitelist array of *symbols*.
  []
end

Any values not returned from these methods will be ignored by Ransack, i.e. they are not authorized.

All four methods can receive a single optional parameter, auth_object. When you call the search or ransack method on your model, you can provide a value for an auth_object key in the options hash which can be used by your own overridden methods.

Here is an example that puts all this together, adapted from this blog post by Ernie Miller. In an Article model, add the following ransackable_attributes class method (preferably private):

class Article < ActiveRecord::Base

  private

  def self.ransackable_attributes(auth_object = nil)
    if auth_object == :admin
      # whitelist all attributes for admin
      super
    else
      # whitelist only the title and body attributes for other users
      super & %w(title body) 
    end
  end
end

Here is example code for the articles_controller:

class ArticlesController < ApplicationController

  def index
    @q = Article.search(params[:q], auth_object: set_ransack_auth_object)
    @articles = @q.result
  end

  private

  def set_ransack_auth_object
    current_user.admin? ? :admin : nil
  end
end

Trying it out in rails console:

> Article
=> Article(id: integer, person_id: integer, title: string, body: text) 

> Article.ransackable_attributes
=> ["title", "body"] 

> Article.ransackable_attributes(:admin)
=> ["id", "person_id", "title", "body"] 

> Article.search(id_eq: 1).result.to_sql
=> SELECT "articles".* FROM "articles"  # Note that search param was ignored!

> Article.search({ id_eq: 1 }, { auth_object: nil }).result.to_sql
=> SELECT "articles".* FROM "articles"  # Search param still ignored!

> Article.search({ id_eq: 1 }, { auth_object: :admin }).result.to_sql
=> SELECT "articles".* FROM "articles"  WHERE "articles"."id" = 1

That's it! Now you know how to whitelist/blacklist various elements in Ransack.

Using Scopes/Class Methods

Continuing on from the preceding section, searching by scopes requires defining a whitelist of ransackable_scopes on the model class. The whitelist should be an array of symbols. By default, all class methods (e.g. scopes) are ignored. Scopes will be applied for matching true values, or for given values if the scope accepts a value:

class Employee < ActiveRecord::Base
  scope :active, ->(boolean = true) { (where active: boolean) }
  scope :salary_gt, ->(amount) { where('salary > ?', amount) }

  # Scopes are just syntactical sugar for class methods, which may also be used:

  def self.hired_since(date)
    where('start_date >= ?', date)
  end

  private

  def self.ransackable_scopes(auth_object = nil)
    if auth_object.try(:admin?)
      # allow admin users access to all three methods
      %i(active hired_since salary_gt)
    else
      # allow other users to search on active and hired_since only
      %i(active hired_since)
    end
  end
end

Employee.search({ active: true, hired_since: '2013-01-01' })

Employee.search({ salary_gt: 100_000 }, { auth_object: current_user })

Grouping queries by OR instead of AND

The default AND grouping can be changed to OR by adding m: 'or' to the query hash.

You can easily try it in your controller code by changing params[:q] in the index action to params[:q].try(:merge, m: 'or') as follows:

def index
  @q = Artist.search(params[:q].try(:merge, m: 'or'))
  @artists = @q.result
end

Normally, if you wanted users to be able to toggle between AND and OR query grouping, you would probably set up your search form so that m was in the URL params hash, but here we assigned m manually just to try it out quickly.

Alternatively, trying it in the Rails console:

artists = Artist.search(name_cont: 'foo', style_cont: 'bar', m: 'or')
=> Ransack::Search<class: Artist, base: Grouping <conditions: [
  Condition <attributes: ["name"], predicate: cont, values: ["foo"]>,
  Condition <attributes: ["style"], predicate: cont, values: ["bar"]>
  ], combinator: or>>

artists.result.to_sql
=> "SELECT \"artists\".* FROM \"artists\"
    WHERE ((\"artists\".\"name\" ILIKE '%foo%'
    OR \"artists\".\"style\" ILIKE '%bar%'))"

The combinator becomes or instead of the default and, and the SQL query becomes WHERE...OR instead of WHERE...AND.

This works with associations as well. Imagine an Artist model that has many Memberships, and many Musicians through Memberships:

artists = Artist.search(name_cont: 'foo', musicians_email_cont: 'bar', m: 'or')
=> Ransack::Search<class: Artist, base: Grouping <conditions: [
  Condition <attributes: ["name"], predicate: cont, values: ["foo"]>,
  Condition <attributes: ["musicians_email"], predicate: cont, values: ["bar"]>
  ], combinator: or>>

artists.result.to_sql
=> "SELECT \"artists\".* FROM \"artists\"
    LEFT OUTER JOIN \"memberships\"
      ON \"memberships\".\"artist_id\" = \"artists\".\"id\"
    LEFT OUTER JOIN \"musicians\"
      ON \"musicians\".\"id\" = \"memberships\".\"musician_id\"
    WHERE ((\"artists\".\"name\" ILIKE '%foo%'
    OR \"musicians\".\"email\" ILIKE '%bar%'))"

Using SimpleForm

If you want to combine form builders of ransack and SimpleForm, just set the RANSACK_FORM_BUILDER environment variable before Rails started, e.g. in config/application.rb before require 'rails/all' and of course use gem 'simple_form' in your Gemfile:

require File.expand_path('../boot', __FILE__)

ENV['RANSACK_FORM_BUILDER'] = '::SimpleForm::FormBuilder'

require 'rails/all'

I18n

Ransack translation files are available in Ransack::Locale. You may also be interested in one of the many translations for Ransack available at http://www.localeapp.com/projects/2999.

Contributions

To support the project:

Use Ransack in your apps, and let us know if you encounter anything that's broken or missing. A failing spec is awesome. A pull request with tests that pass is even better! Before filing an issue or pull request, be sure to read the Contributing Guide.
Spread the word on Twitter, Facebook, and elsewhere if Ransack's been useful to you. The more people who are using the project, the quicker we can find and fix bugs!