# CouchRest::ExtendedDocument: CouchDB, not too close to the metal

CouchRest::ExtendedDocument adds additional functionality to the standard CouchRest Document class such as
setting properties, callbacks, typecasting, and validations.

Note: CouchRest::ExtendedDocument only supports CouchDB 0.10.0 or newer.

## Install

    $ sudo gem install couchrest_extended_document
   
## Usage

### General   

    require 'couchrest_extended_document'

    class Cat < CouchRest::ExtendedDocument

      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 ExtendedDocument (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::ExtendedDocument
      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::ExtendedDocument
      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::ExtendedDocument
      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::ExtendedDocument
      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. ExtendedDocument handles this, along
with casting, by defining the class of the child attributes inside an Array:

    class Cat < CouchRest::ExtendedDocument
      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

ExtendedDocument 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::CastedModel

      property :name, String
      property :purchased, Date
    end

    class Cat << CouchRest::ExtendedDocument
      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 ExtendedDocument (> 1.0.0) supports creating
anonymous classes:

    class Cat << CouchRest::ExtendedDocument
      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.

### Notable Issues

ExtendedDocument 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::ExtendedDocument is compatible with rails and provides some ActiveRecord-like methods.
You might also be interested in the CouchRest companion rails project:
[http://github.com/hpoydar/couchrest-rails](http://github.com/hpoydar/couchrest-rails)      

#### Rails 2.X

In your environment.rb file require the gem as follows:

    Rails::Initializer.run do |config|
      ....
      config.gem "couchrest_extended_document"
      ....
    end

## 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_extended_document](http://rdoc.info/projects/couchrest/couchrest_extended_document)

Check the wiki for documentation and examples [http://wiki.github.com/couchrest/couchrest](http://wiki.github.com/couchrest/couchrest)



## Contact

Please post bugs, suggestions and patches to the bug tracker at [http://github.com/couchrest/couchrest/issues](http://github.com/couchrest/couchrest/issues).

Follow us on Twitter: [http://twitter.com/couchrest](http://twitter.com/couchrest)

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