Ransack

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Ransack is a rewrite of [MetaSearch] (https://github.com/activerecord-hackery/meta_search) 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

In your Gemfile:

gem "ransack"  # Last officially released gem (compatible with Rails 3, 4.0 and 4.1!)

Or if you want to use the latest updates on the master branch:

gem "ransack", github: "activerecord-hackery/ransack"  # Track git repo

If you are on Rails 4.1, you may prefer to use the dedicated Rails 4.1 branch which contains the latest updates, supports only 4.1, and is lighter and somewhat faster:

gem "ransack", github: "activerecord-hackery/ransack", branch: "rails-4.1"

Similarly, if you are on Rails 4.0, you may prefer to use the dedicated Rails 4 branch for the same reasons:

gem "ransack", github: "activerecord-hackery/ransack", branch: "rails-4"

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] (https://github.com/activerecord-hackery/ransack/wiki/Configuration).
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 will 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. Thankfully, 9 times out of 10, sort against the search's base is sufficient, though, as that's generally what's being displayed on your results page.

####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])
end

####In your view

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

#####Ransack's search_form_for helper replaces form_for for creating the view search form:

<%= search_form_for @q do |f| %>
  <%= f.label :name_cont %>
  <%= f.search_field :name_cont %>
  <%= f.label :articles_title_start %>
  <%= f.search_field :articles_title_start %>
  <%= f.submit %>
<% end %>

cont (contains) and start (starts with) are just two of the available search predicates. See [Constants] (https://github.com/activerecord-hackery/ransack/blob/master/lib/ransack/constants.rb) for a full list and the [wiki] (https://github.com/activerecord-hackery/ransack/wiki/Basic-Searching) 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| %>

#####Ransack's sort_link helper is useful for creating 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])

has_many and belongs_to associations

You can easily use Ransack to search in associated objects.

Given you have these associations ...

class Employee < ActiveRecord::Base
  belongs_to :supervisor

  # has attribute 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
    @search = Supervisor.search(params[:q])
    @supervisors = @search.result.includes(:department, :employees)
  end
end

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

<%= search_form_for @search 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_last_name_cont %>
  <%= f.search_field :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] (https://github.com/activerecord-hackery/ransack/wiki/Using-Ransackers). Feel free to contribute working ransacker code examples to the wiki!

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!

todddickerson/ransack