Queryable

Queryable is a mixin that allows you to easily define query objects with chainable scopes.

Scopes

Scopes serve to encapsulate reusable business rules, a method is defined with the selected name and block (or proc)

class CustomersQuery
  include Queryable

  scope(:recent) { desc(:logged_in_at) }

  scope :active, ->{ where(status: 'active') }

  scope :favourite_brand do |product, brand|
    where("favourites.#{product}": brand)
  end

  def current
    recent.active
  end

  def miller_fans
    favourite_brand(:beer, :Miller)
  end
end


CustomerQuery.new(shop.customers).miller_fans

Delegation

By default most Array methods are delegated to the internal query. It's possible to delegate extra methods to the query by calling delegate.

class CustomersQuery
  include Queryable

  delegate :update_all, :destroy_all, :exists?
end

Delegate and Chain

Sometimes you want to delegate a method to the internal query, but continue working with the query object like if you were calling scopes.

You can achieve that using delegate_and_chain, which will delegate the method call, assign the return value as the internal query, and return the query object.

class CustomersQuery
  include Queryable

  delegate_and_chain :where, :order_by
end

Advantages

• Query objects are easy to understand.
• You can inherit, mixin, and chain queries in a very natural way.
• Increased testability, pretty close to being ORM/ODM agnostic.

Basic Usage

If you are using Mongoid or ActiveRecord, you might want to try the Queryable::Mongoid and Queryable::ActiveRecord modules that already take care of delegating and chaining most of the methods in the underlying queries.

class CustomersQuery
  include Queryable::Mongoid
end

CustomersQuery.new.where(:amount_purchased.gt => 2).active.asc(:logged_in_at)

This modules also include all the optional modules. If you would like to opt-out of the other modules you can follow the approach in the Notes section.

Advanced Usage

There are three opt-in modules that can help you when creating query objects. These modules would need to be manually required during app initialization or wherever necessary (in Rails, config/initializers).

DefaultQuery

Provides default initialization for query objects, by attempting to infer the class name of the default collection for the query, and it also provides a queryable method to specify it.

require 'queryable/default_query'

def CustomersQuery
  include Queryable
  include Queryable::DefaultQuery
end

def OldCustomersQuery < CustomersQuery
  queryable ArchivedCustomers
end

CustomersQuery.new.queryable == Customer.all
OldCustomersQuery.new.queryable == ArchivedCustomers.all

If you want to use common base objects for your queries, you may want want to delay the automatic inference:

class BaseQuery
  include Queryable
  include Queryable::DefaultQuery

  queryable false
end

class CustomersQuery < BaseQuery
end

CustomersQuery.new.queryable == Customer.all

DefaultScope

Allows to define default scopes in query objects, and inherit them in query object subclasses.

require 'queryable/default_scope'

def CustomersQuery
  include Queryable
  include Queryable::DefaultScope
  include Queryable::DefaultQuery

  default_scope :active
  scope :active, -> { where(:last_purchase.gt => 7.days.ago) }
end

def BigCustomersQuery < CustomersQuery
  default_scope :big_spender
  scope :big_spender, -> { where(:total_expense.gt => 9999999) }
end

CustomersQuery.new.queryable == Customer.where(:last_purchase.gt => 7.days.ago)

BigCustomersQuery.new.queryable ==
Customer.where(:last_purchase.gt => 7.days.ago, :total_expense.gt => 9999999)

Chainable

While scopes are great because of their terseness, they can be limiting because the block executes in the context of the internal query, so methods, constants, and variables of the Queryable are not accessible.

For those cases, you can use a normal method, and then chain it. Chainable will take care of setting the return value of the method as the internal query, and return self at the end to make the method chainable.

class CustomersQuery
  include Queryable
  include Queryable::Chainable

  chain :active, :recent

  def active
    where(status: 'active')
  end

  def recent
    queryable.desc(:logged_in_at)
  end

  chain def search(field_values)
    field_values.inject(queryable) { |query, (field, value)|
      query.where(field => /#{value}/i)
    }
  end

  def search_in_active(field_values)
    search(field_values).active
  end
end


CustomerQuery.new(shop.customers).miller_fans.search_in_current(last_name: 'M')

Notes

To avoid repetition, it's a good idea to create a BaseQuery object to contain both the modules inclusion, and common scopes you may reuse.

require 'queryable/chainable'
require 'queryable/default_scope'
require 'queryable/default_query'

def BaseQuery
  include Queryable
  include Queryable::Chainable
  include Queryable::DefaultScope
  include Queryable::DefaultQuery

  # If you want to be concise:
  include Queryable::DefaultQuery, Queryable::DefaultScope, Queryable::Chainable, Queryable

  queryable false

  scope :recent, ->{ where(:created_at.gt => 1.week.ago) }
end

def CustomersQuery < BaseQuery
...
end

Testing

You can check the specs of the project to check how to test query objects without even having to require the ORM/ODM, or you can test by requiring your ORM/ODM and executing queries as usual.

RDocs

You can view the Queryable documentation in RDoc format here:

http://rubydoc.info/github/ElMassimo/queryable/master/frames

License

Copyright (c) 2014 Máximo Mussini

Permission is hereby granted, free of charge, to any person obtaining
a copy of this software and associated documentation files (the
"Software"), to deal in the Software without restriction, including
without limitation the rights to use, copy, modify, merge, publish,
distribute, sublicense, and/or sell copies of the Software, and to
permit persons to whom the Software is furnished to do so, subject to
the following conditions:

The above copyright notice and this permission notice shall be
included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE
LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION
OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION
WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.