ajax-datatables-rails

Important

Datatables recently released version 1.10 (which includes a new API and features) and deprecated version 1.9.

This gem is targeted at Datatables version 1.10 and up.

Description

Datatables is a nifty jquery plugin that adds the ability to paginate, sort, and search your html tables. When dealing with large tables (more than a couple hundred rows) however, we run into performance issues. These can be fixed by using server-side pagination, but this breaks some datatables functionality.

ajax-datatables-rails is a wrapper around datatable's ajax methods that allow synchronization with server-side pagination in a rails app. It was inspired by this Railscast. I needed to implement a similar solution in a couple projects I was working on, so I extracted a solution into a gem.

ORM support

Currently AjaxDatatablesRails only supports ActiveRecord as ORM for performing database queries.

Adding support for Sequel, Mongoid and MongoMapper is a planned feature for this gem. If you'd be interested in contributing to speed development, please open an issue and get in touch.

Installation

Add these lines to your application's Gemfile:

gem 'jquery-datatables-rails'
gem 'ajax-datatables-rails'

And then execute:

$ bundle

The jquery-datatables-rails gem is listed as a convenience, to ease adding jQuery dataTables to your Rails project. You can always add the plugin assets manually via the assets pipeline. If you decide to use the jquery-datatables-rails gem, please refer to its installation instructions here.

Usage

The following examples assume that we are setting up ajax-datatables-rails for an index page of users from a User model, and that we are using postgresql as our db, because you should be using it, if not, please refer to the Searching on non text-based columns entry in the Additional Notes section.

Generate

Run the following command:

$ rails generate datatable User

This will generate a file named user_datatable.rb in app/datatables. Open the file and customize in the functions as directed by the comments.

Take a look here for an explanation about the generator syntax.

Build the View

You should always start by the single source of truth, which is your html view. Suppose we need to render a users table and display: first name, last name, and bio for each user.

Something like this:

First Name	Last Name	Brief Bio
John	Doe	Is your default user everywhere
Jane	Doe	Is John's wife
James	Doe	Is John's brother and best friend

Set up an html <table> with a <thead> and <tbody>
Add in your table headers if desired
Don't add any rows to the body of the table, datatables does this automatically
Add a data attribute to the <table> tag with the url of the JSON feed, in our case is the users_path as we're pointing to the UsersController#index action

<table id="users-table", data-source="<%= users_path(format: :json) %>">
  <thead>
    <tr>
      <th>First Name</th>
      <th>Last Name</th>
      <th>Brief Bio</th>
    </tr>
  </thead>
  <tbody>
  </tbody>
</table>

Customize the generated Datatables class

def view_columns
  # Declare strings in this format: ModelName.column_name
  # or in aliased_join_table.column_name format
  @view_columns ||= []
end

In this method, add a list of the model(s) columns mapped to the data you need to present. In this case: first_name, last_name and bio.

This gives us:

def view_columns
  @view_columns ||= %w(User.first_name User.last_name User.bio)
  # this is equal to:
  # @view_columns ||= ['User.first_name', 'User.last_name', 'User.bio']
end

See here for notes about the view_columns settings (if using something different from postgre).
Read these notes about considerations for the view_columns method.

Map data

def data
  records.map do |record|
    [
        # comma separated list of the values for each cell of a table row
        # example: record.attribute,
      ]
  end
end

This method builds a 2d array that is used by datatables to construct the html table. Insert the values you want on each column.

def data
  records.map do |record|
    [
      record.first_name,
      record.last_name,
      record.bio
    ]
  end
end

See here if you need to use view helpers in the returned 2d array, like link_to, mail_to, resource_path, etc.

Get Raw Records

def get_raw_records
  # insert query here
end

This is where your query goes.

def get_raw_records
  # suppose we need all User records
  # Rails 4+
  User.all
  # Rails 3.x
  # User.scoped
end

Obviously, you can construct your query as required for the use case the datatable is used. Example: User.active.with_recent_messages.

IMPORTANT: Make sure to return an ActiveRecord::Relation object as the end product of this method.

Why? Because the result from this method, will be chained (for now) to ActiveRecord methods for sorting, filtering and pagination.

Associated and nested models

The previous example has only one single model. But what about if you have some associated nested models and in a report you want to show fields from these tables.

Take an example that has an Event, Course, Coursetype, Allocation, Teacher, Contact, Competency and CompetencyType models. We want to have a datatables report which has the following column:

        'coursetypes.name',
        'courses.name',
        'events.title',
        'events.event_start',
        'events.event_end',
        'contacts.full_name',
        'competency_types.name',
        'events.status'

We want to sort and search on all columns of the list. The related definition would be:

  def view_columns
    @view_columns ||= [
        'Coursetype.name',
        'Course.name',
        'Event.title',
        'Event.event_start',
        'Event.event_end',
        'Contact.last_name',
        'CompetencyType.name',
        'Event.status'
    ]
  end

  def get_raw_records
     Event.joins(
      { course: :coursetype },
      { allocations: {
          teacher: [:contact, {competencies: :competency_type}]
        }
      }).distinct
  end

Some comments for the above code:

In the get_raw_records method we have quite a complex query having one to many and may to many associations using the joins ActiveRecord method. The joins will generate INNER JOIN relations in the SQL query. In this case, we do not include all event in the report if we have events which is not associated with any model record from the relation.
To have all event records in the list we should use the .includes method, which generate LEFT OUTER JOIN relation of the SQL query. IMPORTANT: Make sure to append .references(:related_model) with any associated model. That forces the eager loading of all the associated models by one SQL query, and the search condition for any column works fine. Otherwise the :recordsFiltered => filter_records(get_raw_records).count(:all) will generate 2 SQL queries (one for the Event model, and then another for the associated tables). The :recordsFiltered => filter_records(get_raw_records).count(:all) will use only the first one to return from the ActiveRecord::Relation object in get_raw_records and you will get an error message of Unknown column 'yourtable.yourfield' in 'where clause' in case the search field value is not empty.

So the query using the .includes() method is:

  def get_raw_records
     Event.includes(
      { course: :coursetype },
      { allocations: {
          teacher: [:contact, { competencies: :competency_type }]
        }
      }
      ).references(:course).distinct
  end

Setup the Controller action

Set the controller to respond to JSON

def index
  respond_to do |format|
    format.html
    format.json { render json: UserDatatable.new(view_context) }
  end
end

Don't forget to make sure the proper route has been added to config/routes.rb.

Wire up the Javascript

Finally, the javascript to tie this all together. In the appropriate coffee file:

# users.coffee

$ ->
  $('#users-table').dataTable
    processing: true
    serverSide: true
    ajax: $('#users-table').data('source')
    pagingType: 'full_numbers'
    # optional, if you want full pagination controls.
    # Check dataTables documentation to learn more about
    # available options.

or, if you're using plain javascript:

// users.js

jQuery(document).ready(function() {
  $('#users-table').dataTable({
    "processing": true,
    "serverSide": true,
    "ajax": $('#users-table').data('source'),
    "pagingType": "full_numbers",
    // optional, if you want full pagination controls.
    // Check dataTables documentation to learn more about
    // available options.
  });
});

Additional Notes

Columns syntax

Since version 0.3.0, we are implementing a pseudo code way of declaring the array columns to use when querying the database.

Example. Suppose we have the following models: User, PurchaseOrder, Purchase::LineItem and we need to have several columns from those models available in our datatable to search and sort by.

# we use the ModelName.column_name notation to declare our columns

def view_columns
  @view_columns ||= [
    'User.first_name',
    'User.last_name',
    'PurchaseOrder.number',
    'PurchaseOrder.created_at',
    'Purchase::LineItem.quantity',
    'Purchase::LineItem.unit_price',
    'Purchase::LineItem.item_total'
  ]
end

What if the datatable itself is namespaced?

Example: what if the datatable is namespaced into an Admin module?

module Admin
  class PurchasesDatatable < AjaxDatatablesRails::Base
  end
end

Taking the same models and columns, we would define it like this:

def view_columns
  @view_columns ||= [
    '::User.first_name',
    '::User.last_name',
    '::PurchaseOrder.number',
    '::PurchaseOrder.created_at',
    '::Purchase::LineItem.quantity',
    '::Purchase::LineItem.unit_price',
    '::Purchase::LineItem.item_total'
  ]
end

Pretty much like you would do it, if you were inside a namespaced controller.

Searching on non text-based columns

It always comes the time when you need to add a non-string/non-text based column to the @view_columns array, so you can perform searches against these column types (example: numeric, date, time).

We recently added the ability to (automatically) typecast these column types and have this scenario covered. Please note however, if you are using something different from postgresql (with the :pg gem), like mysql or sqlite, then you need to add an initializer in your application's config/initializers directory.

If you don't perform this step (again, if using something different from postgresql), your database will complain that it does not understand the default typecast used to enable such searches.

Configuration initializer

You have two options to create this initializer:

use the provided (and recommended) generator (and then just edit the file);
create the file from scratch.

To use the generator, from the terminal execute:

$ bundle exec rails generate datatable:config

Doing so, will create the config/initializers/ajax_datatables_rails.rb file with the following content:

AjaxDatatablesRails.configure do |config|
  # available options for db_adapter are: :pg, :mysql, :mysql2, :sqlite, :sqlite3
  # config.db_adapter = :pg

  # available options for orm are: :active_record, :mongoid
  # config.orm = :active_record
end

Uncomment the config.db_adapter line and set the corresponding value to your database and gem. This is all you need.

Uncomment the config.orm line to set active_record or mongoid if included in your project. It defaults to active_record.

If you want to make the file from scratch, just copy the above code block into a file inside the config/initializers directory.

Using view helpers

Sometimes you'll need to use view helper methods like link_to, h, mailto, edit_resource_path in the returned JSON representation returned by the data method.

To have these methods available to be used, this is the way to go:

class MyCustomDatatable < AjaxDatatablesRails::Base
  # either define them one-by-one
  def_delegator :@view, :link_to
  def_delegator :@view, :h
  def_delegator :@view, :mail_to

  # or define them in one pass
  def_delegators :@view, :link_to, :h, :mailto, :edit_resource_path, :other_method

  # now, you'll have these methods available to be used anywhere
  # example: mapping the 2d jsonified array returned.
  def data
    records.map do |record|
      [
        link_to(record.fname, edit_resource_path(record)),
        mail_to(record.email),
        # other attributes
      ]
    end
  end
end

Options

An AjaxDatatablesRails::Base inherited class can accept an options hash at initialization. This provides room for flexibility when required. Example:

class UnrespondedMessagesDatatable < AjaxDatatablesRails::Base
  # customized methods here
end

datatable = UnrespondedMessagesDatatable.new(view_context,
  { :foo => { :bar => Baz.new }, :from => 1.month.ago }
)

So, now inside your class code, you can use those options like this:

# let's see an example
def from
  @from ||= options[:from].beginning_of_day
end

def to
  @to ||= Date.today.end_of_day
end

def get_raw_records
  Message.unresponded.where(received_at: from..to)
end

Generator Syntax

Also, a class that inherits from AjaxDatatablesRails::Base is not tied to an existing model, module, constant or any type of class in your Rails app. You can pass a name to your datatable class like this:

$ rails generate datatable users
# returns a users_datatable.rb file with a UsersDatatable class

$ rails generate datatable contact_messages
# returns a contact_messages_datatable.rb file with a ContactMessagesDatatable class

$ rails generate datatable UnrespondedMessages
# returns an unresponded_messages_datatable.rb file with an UnrespondedMessagesDatatable class

In the end, it's up to the developer which model(s), scope(s), relationship(s) (or else) to employ inside the datatable class to retrieve records from the database.

Tutorial

Tutorial for Integrating ajax-datatable-rails, on Rails 4.

IMPORTANT: this tutorial is deprecated on version 0.4.0, and applies to version 0.3.0 and below.

Part-1 The-Installation

Part 2 The Datatables with ajax functionality

The complete project code for this tutorial series is available on github.

Contributing

Fork it
Create your feature branch (git checkout -b my-new-feature)
Commit your changes (git commit -am 'Added some feature')
Push to the branch (git push origin my-new-feature)
Create new Pull Request

nicholette / ajax-datatables-rails