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Queryable is a mixin that allows you to easily define query objects with chainable 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_fansBy 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?
endSometimes 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- 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.
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.
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).
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.allIf 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.allAllows 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)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')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
...
endYou 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.
You can view the Queryable documentation in RDoc format here:
http://rubydoc.info/github/ElMassimo/queryable/master/frames
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.