9.9 KiB
CouchRest Model: CouchDB, close to shiny metal with rounded edges
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 only supports CouchDB 0.10.0 or newer.
Install
$ sudo gem install couchrest_model
General Usage
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!
Properties
Only attributes with a property definition will be stored be CouchRest Model (as opposed to a normal CouchRest Document which will store everything). To help prevent confusion, a property should be considered as the definition of an attribute. An attribute must be associated with a property, but a property may not have any attributes associated if none have been set.
In its simplest form, a property
will only create a getter and setter passing all attribute data directly to the database. Assuming the attribute
provided responds to to_json, there will not be any problems saving it, but when loading the
data back it will either be a string, number, array, or hash:
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!
Booleans or TrueClass will also 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.
Defining a property as read-only will mean that its value is set only when read from the
database and that it will not have a setter method. 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!
Property Arrays
An attribute may also 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.
Casted Models
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', :purchases => 1.month.ago}])
@cat.toys.first.class == CatToy
@cat.toys.first.name == 'mouse'
Additionally, any hashes sent to the property will automatically be converted:
@cat.toys << {:name => 'catnip ball'}
@cat.toys.last.is_a?(CatToy) # True!
Of course, 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, the latest version of CouchRest Model (> 1.0.0) supports creating anonymous classes:
class Cat << CouchRest::Model::Base
property :name, String
property :toys do |toy|
toy.property :name, String
toy.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'
Using this method of anonymous classes will only create arrays of objects.
Assocations
Two types at the moment:
belongs_to :person
collection_of :tags
TODO: Document properly!
Validations
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!
Notable Issues
CouchRest Model uses active_support for some of its internals. Ensure you have a stable active support gem installed or at least 3.0.0.beta4.
JSON gem versions 1.4.X are kown to cause problems with stack overflows and general badness. Version 1.2.4 appears to work fine.
Ruby on Rails
CouchRest Model is compatible with rails and provides some ActiveRecord-like methods.
The CouchRest companion rails project http://github.com/hpoydar/couchrest-rails is great for provided default connection details for your database. At the time of writting however it does not provide explicit support for CouchRest Model.
CouchRest Model and the original CouchRest ExtendedDocument do not share the same namespace, as such you should not have any problems using them both at the same time. This might help with migrations.
Rails 3.0
In your Gemfile require the gem with a simple line:
gem "couchrest_model"
Testing
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).
Docs
API: http://rdoc.info/projects/couchrest/couchrest_model
Check the wiki for documentation and examples http://wiki.github.com/couchrest/couchrest_model
Contact
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