CouchRest Models adds additional functionality to the standard CouchRest Document class such as setting properties, callbacks, typecasting, and validations.
Originally called ExtendedDocument, the new Model structure uses ActiveModel, part of Rails 3, for validations and callbacks.
If your project is still running Rails 2.3, you'll have to continue using ExtendedDocument as it is not possible to load ActiveModel into programs that do not use ActiveSupport 3.0.
CouchRest Model is only tested on CouchDB 1.0.0 or newer.
$ sudo gem install couchrest_model
If you're using bundler, just define a line similar to the following in your project's Gemfile:
gem 'couchrest_model'
You might also consider using the latest git repository. All tests should pass in the master code branch but no guarantees!
gem 'couchrest_model', :git => 'git://github.com/couchrest/couchrest_model.git'
There is currently no standard way for telling CouchRest Model how it should access your database, this is something we're still working on. For the time being, the easiest way is to set a COUCHDB_DATABASE global variable to an instance of CouchRest Database, and call use_database COUCHDB_DATABASE in each model.
TODO: Add an example!
CouchRest Model now comes with a Gemfile to help with development. If you want to make changes to the code, download a copy then run:
bundle install
That should set everything up for rake spec to be run correctly. Update the couchrest_model.gemspec if your alterations
use different gems.
$ rails generate model person --orm=couchrest_model
Try some of these gems that add extra funcionality to couchrest_model:
- memories - object versioning using attachments (Matt Parker)
- couch_publish - versioned state machine for draft and published documents (Matt Parker)
- couch_photo - attach images to documents with variations (Matt Parker)
- copycouch - single document replication on documents (Matt Parker)
- recloner - clone documents easily (Matt Parker)
If you have an extension that you'd us to add to this list, please get in touch!
require 'couchrest_model'
class Cat < CouchRest::Model::Base
property :name, String
property :lives, Integer, :default => 9
property :nicknames, [String]
timestamps!
view_by :name
end
@cat = Cat.new(:name => 'Felix', :nicknames => ['so cute', 'sweet kitty'])
@cat.new? # true
@cat.save
@cat['name'] # "Felix"
@cat.nicknames << 'getoffdamntable'
@cat = Cat.new
@cat.update_attributes(:name => 'Felix', :random_text => 'feline')
@cat.new? # false
@cat.random_text # Raises error!
A property is the definition of an attribute, it describes what the attribute is called, how it should
be type casted and other options such as the default value. These replace your typical
add_column methods found in relational database migrations.
Attributes with a property definition will have setter and getter methods defined for them. Any other attibute can be set in the same way you'd update a Hash, this funcionality is inherited from CouchRest Documents.
Here are a few examples of the way properties are used:
class Cat < CouchRest::Model::Base
property :name
property :birthday
end
@cat = Cat.new(:name => 'Felix', :birthday => 2.years.ago)
@cat.name # 'Felix'
@cat.birthday.is_a?(Time) # True!
@cat.save
@cat = Cat.find(@cat.id)
@cat.name # 'Felix'
@cat.birthday.is_a?(Time) # False!
Properties create getters and setters similar to the following:
def name
read_attribute('name')
end
def name=(value)
write_attribute('name', value)
end
Properties can also have a type which will be used for casting data retrieved from CouchDB when the attribute is set:
class Cat < CouchRest::Model::Base
property :name, String
property :last_fed_at, Time
end
@cat = Cat.new(:name => 'Felix', :last_fed_at => 10.minutes.ago)
@cat.last_fed_at.is_a?(Time) # True!
@cat.save
@cat = Cat.find(@cat.id)
@cat.last_fed_at < 20.minutes.ago # True!
Boolean or TrueClass types will create a getter with question mark at the end:
class Cat < CouchRest::Model::Base
property :awake, TrueClass, :default => true
end
@cat.awake? # true
Adding the +:default+ option will ensure the attribute always has a value.
A read-only property will only have a getter method, and its value is set when the document
is read from the database. You can however update a read-only attribute using the write_attribute method:
class Cat < CouchRest::Model::Base
property :name, String
property :lives, Integer, :default => 9, :readonly => true
def fall_off_balcony!
write_attribute(:lives, lives - 1)
save
end
end
@cat = Cat.new(:name => "Felix")
@cat.fall_off_balcony!
@cat.lives # Now 8!
Mass assigning attributes is also possible in a similar fashion to ActiveRecord:
@cat.attributes = { :name => "Felix" }
@cat.save
Is the same as:
@cat.update_attributes(:name => "Felix")
By default, attributes without a property will not be updated via the #attributes= method. This provents useless data being passed to database, for example from an HTML form. However, if you would like truely
dynamic attributes, the mass_assign_any_attribute configuration option when set to true will
store everything you put into the Base#attributes= method.
An attribute may contain an array of data. CouchRest Model handles this, along with casting, by defining the class of the child attributes inside an Array:
class Cat < CouchRest::Model::Base
property :name, String
property :nicknames, [String]
end
By default, the array will be ready to use from the moment the object as been instantiated:
@cat = Cat.new(:name => 'Fluffy')
@cat.nicknames << 'Buffy'
@cat.nicknames == ['Buffy']
When anything other than a string is set as the class of a property, the array will be converted
into special wrapper called a CastedArray. If the child objects respond to the casted_by method
(such as those created with CastedModel, below) it will contain a reference to the parent.
CouchRest Model allows you to take full advantage of CouchDB's ability to store complex documents and retrieve them using the CastedModel module. Simply include the module in a Hash (or other model that responds to the [] and []= methods) and set any properties you'd like to use. For example:
class CatToy < Hash
include CouchRest::Model::CastedModel
property :name, String
property :purchased, Date
end
class Cat < CouchRest::Model::Base
property :name, String
property :toys, [CatToy]
end
@cat = Cat.new(:name => 'Felix', :toys => [{:name => 'mouse', :purchased => 1.month.ago}])
@cat.toys.first.class == CatToy
@cat.toys.first.name == 'mouse'
Any hashes sent to the property will automatically be converted:
@cat.toys << {:name => 'catnip ball'}
@cat.toys.last.is_a?(CatToy) # True!
To use your own classes they must be defined before the parent uses them otherwise Ruby will bring up a missing constant error. To avoid this, or if you have a really simple array of data you'd like to model, CouchRest Model supports creating anonymous classes:
class Cat < CouchRest::Model::Base
property :name, String
property :toys do
property :name, String
property :rating, Integer
end
end
@cat = Cat.new(:name => 'Felix', :toys => [{:name => 'mouse', :rating => 3}, {:name => 'catnip ball', :rating => 5}])
@cat.toys.last.rating == 5
@cat.toys.last.name == 'catnip ball'
Anonymous classes will only create arrays of objects. If you're more of the traditional type, a block parameter can be provided allowing you to use this variable before each method call inside the anonymous class. This is useful if you need to access variables outside of the block.
Two types at the moment:
belongs_to :person
collection_of :tags
This is a somewhat controvesial feature of CouchRest Model that some document database purists may cringe at. CouchDB does not yet povide many features to support relationships between documents but the fact of that matter is that its a very useful paradigm for modelling data systems.
In the near future we hope to add support for a has_many relationship that takes of the Linked Documents feature that arrived in CouchDB 0.11.
Creates a property in the document with _id added to the end of the name of the foreign model with getter and setter methods to access the model.
Example:
class Cat < CouchRest::Model::Base
belongs_to :mother
property :name
end
kitty = Cat.new(:name => "Felix")
kitty.mother = Mother.find_by_name('Sophie')
Providing a object to the setter, mother in the example will automagically update the mother_id attribute. Retrieving the data later is just as expected:
kitty = Cat.find_by_name "Felix"
kitty.mother.name == 'Sophie'
Belongs_to accepts a few options to add a bit more felxibility:
:class_name- the camel case string name of the class used to load the model.:foreign_key- the name of the property to use instead of the attribute name with_idon the end.:proxy- a string that when evaluated provides a proxy model that responds to#get.
The last option, :proxy is a feature currently in testing that allows objects to be loaded from a proxy class, such as ClassProxy. For example:
class Invoice < CouchRest::Model::Base
attr_accessor :company
belongs_to :project, :proxy => 'self.company.projects'
end
A project instance in this scenario would need to be loaded by calling #get(project_id) on self.company.projects in the scope of an instance of the Invoice. We hope to document and work on this powerful feature in the near future.
A collection_of relationship is much like belongs_to except that rather than just one foreign key, an array of foreign keys can be stored. This is one of the great features of a document database. This relationship uses a proxy object to automatically update two arrays; one containing the objects being used, and a second with the foreign keys used to the find them.
The best example of this in use is with Labels:
class Invoice < CouchRest::Model::Base
collection_of :labels
end
invoice = Invoice.new
invoice.labels << Label.get('xyz')
invoice.labels << Label.get('abc')
invoice.labels.map{|l| l.name} # produces ['xyz', 'abc']
See the belongs_to relationship for the options that can be used. Note that this isn't especially efficient, a get is performed for each model in the array. As with a has_many relationship, we hope to be able to take advantage of the Linked Documents feature to avoid multiple requests.
CouchRest Model automatically includes the new ActiveModel validations, so they should work just as the traditional Rails validations. For more details, please see the ActiveModel::Validations documentation.
CouchRest Model adds the possibility to check the uniqueness of attributes using the validates_uniqueness_of class method, for example:
class Person < CouchRest::Model::Base
property :title, String
validates_uniqueness_of :title
end
The uniqueness validation creates a new view for the attribute or uses one that already exists. You can
specify a different view using the :view option, useful for when the unique_id is specified and
you'd like to avoid the typical RestClient Conflict error:
unique_id :code
validates_uniqueness_of :code, :view => 'all'
Given that the uniqueness check performs a request to the database, it is also possible to include a :proxy parameter. This allows you to call a method on the document and provide an alternate proxy object.
Examples:
# Same as not including proxy:
validates_uniqueness_of :title, :proxy => 'class'
# Person#company.people provides a proxy object for people
validates_uniqueness_of :title, :proxy => 'company.people'
A really interesting use of :proxy and :view together could be where you'd like to ensure the ID is unique between several types of document. For example:
class Product < CouchRest::Model::Base
property :code
validates_uniqueness_of :code, :view => 'by_product_code'
view_by :product_code, :map => "
function(doc) {
if (doc['couchrest-type'] == 'Product' || doc['couchrest-type'] == 'Project') {
emit(doc['code']);
}
}
"
end
class Project < CouchRest::Model::Base
property :code
validates_uniqueness_of :code, :view => 'by_product_code', :proxy => 'Product'
end
Pretty cool!
CouchRest Model supports a few configuration options. These can be set either for the whole Model code base or for a specific model of your chosing. To configure globally, provide something similar to the following in your projects loading code:
CouchRest::Model::Base.configure do |config|
config.mass_assign_any_attribute = true
config.model_type_key = 'couchrest-type'
end
To set for a specific model:
class Cat < CouchRest::Model::Base mass_assign_any_attribute true end
Options currently avilable are:
mass_assign_any_attribute- false by default, when true any attribute may be updated via the update_attributes or attributes= methods.model_type_key- 'couchrest-type' by default, is the name of property that holds the class name of each CouchRest Model.
None at the moment...
The most complete documentation is the spec/ directory. To validate your CouchRest install, from the project root directory run rake, or autotest (requires RSpec and optionally ZenTest for autotest support).
API: http://rdoc.info/projects/couchrest/couchrest_model
Check the wiki for documentation and examples http://wiki.github.com/couchrest/couchrest_model
Please post bugs, suggestions and patches to the bug tracker at http://github.com/couchrest/couchrest_model/issues.
Follow us on Twitter: http://twitter.com/couchrest
Also, check http://twitter.com/#search?q=%23couchrest