couchrest_model/lib/couchrest/core/model.rb

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require 'rubygems'
require 'extlib'
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require 'digest/md5'
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# = CouchRest::Model - ORM, the CouchDB way
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module CouchRest
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# = CouchRest::Model - ORM, the CouchDB way
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#
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# CouchRest::Model provides an ORM-like interface for CouchDB documents. It
# avoids all usage of <tt>method_missing</tt>, and tries to strike a balance
# between usability and magic. See CouchRest::Model#view_by for
# documentation about the view-generation system.
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#
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# ==== Example
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#
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# This is an example class using CouchRest::Model. It is taken from the
# spec/couchrest/core/model_spec.rb file, which may be even more up to date
# than this example.
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#
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# class Article < CouchRest::Model
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# use_database CouchRest.database!('http://localhost:5984/couchrest-model-test')
# unique_id :slug
#
# view_by :date, :descending => true
# view_by :user_id, :date
#
# view_by :tags,
# :map =>
# "function(doc) {
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# if (doc['couchrest-type'] == 'Article' && doc.tags) {
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# doc.tags.forEach(function(tag){
# emit(tag, 1);
# });
# }
# }",
# :reduce =>
# "function(keys, values, rereduce) {
# return sum(values);
# }"
#
# key_writer :date
# key_reader :slug, :created_at, :updated_at
# key_accessor :title, :tags
#
# timestamps!
#
# before(:create, :generate_slug_from_title)
# def generate_slug_from_title
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# self['slug'] = title.downcase.gsub(/[^a-z0-9]/,'-').squeeze('-').gsub(/^\-|\-$/,'')
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# end
# end
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#
# ==== Examples of finding articles with these views:
#
# * All the articles by Barney published in the last 24 hours. Note that we
# use <tt>{}</tt> as a special value that sorts after all strings,
# numbers, and arrays.
#
# Article.by_user_id_and_date :startkey => ["barney", Time.now - 24 * 3600], :endkey => ["barney", {}]
#
# * The most recent 20 articles. Remember that the <tt>view_by :date</tt>
# has the default option <tt>:descending => true</tt>.
#
# Article.by_date :count => 20
#
# * The raw CouchDB view reduce result for the custom <tt>:tags</tt> view.
# In this case we'll get a count of the number of articles tagged "ruby".
#
# Article.by_tags :key => "ruby", :reduce => true
#
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class Model < Hash
# instantiates the hash by converting all the keys to strings.
def initialize keys = {}
super()
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apply_defaults
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keys.each do |k,v|
self[k.to_s] = v
end
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cast_keys
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unless self['_id'] && self['_rev']
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self['couchrest-type'] = self.class.to_s
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end
end
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# this is the CouchRest::Database that model classes will use unless
# they override it with <tt>use_database</tt>
cattr_accessor :default_database
class_inheritable_accessor :casts
class_inheritable_accessor :default_obj
class_inheritable_accessor :class_database
class_inheritable_accessor :generated_design_doc
class_inheritable_accessor :design_doc_slug_cache
class_inheritable_accessor :design_doc_fresh
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class << self
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# override the CouchRest::Model-wide default_database
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def use_database db
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self.class_database = db
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end
# returns the CouchRest::Database instance that this class uses
def database
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self.class_database || CouchRest::Model.default_database
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end
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# Load a document from the database by id
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def get id
doc = database.get id
new(doc)
end
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# Load all documents that have the "couchrest-type" field equal to the
# name of the current class. Take thes the standard set of
# CouchRest::Database#view options.
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def all opts = {}
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self.generated_design_doc ||= default_design_doc
unless design_doc_fresh
refresh_design_doc
end
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view_name = "#{design_doc_slug}/all"
raw = opts.delete(:raw)
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fetch_view_with_docs(view_name, opts, raw)
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end
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# Cast a field as another class. The class must be happy to have the
# field's primitive type as the argument to it's constucture. Classes
# which inherit from CouchRest::Model are happy to act as sub-objects
# for any fields that are stored in JSON as object (and therefore are
# parsed from the JSON as Ruby Hashes).
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def cast field, opts = {}
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self.casts ||= {}
self.casts[field.to_s] = opts
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end
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# Defines methods for reading and writing from fields in the document.
# Uses key_writer and key_reader internally.
def key_accessor *keys
key_writer *keys
key_reader *keys
end
# For each argument key, define a method <tt>key=</tt> that sets the
# corresponding field on the CouchDB document.
def key_writer *keys
keys.each do |method|
key = method.to_s
define_method "#{method}=" do |value|
self[key] = value
end
end
end
# For each argument key, define a method <tt>key</tt> that reads the
# corresponding field on the CouchDB document.
def key_reader *keys
keys.each do |method|
key = method.to_s
define_method method do
self[key]
end
end
end
def default
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self.default_obj
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end
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def set_default hash
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self.default_obj = hash
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end
# Automatically set <tt>updated_at</tt> and <tt>created_at</tt> fields
# on the document whenever saving occurs. CouchRest uses a pretty
# decent time format by default. See Time#to_json
def timestamps!
before(:create) do
self['updated_at'] = self['created_at'] = Time.now
end
before(:update) do
self['updated_at'] = Time.now
end
end
# Name a method that will be called before the document is first saved,
# which returns a string to be used for the document's <tt>_id</tt>.
# Because CouchDB enforces a constraint that each id must be unique,
# this can be used to enforce eg: uniq usernames. Note that this id
# must be globally unique across all document types which share a
# database, so if you'd like to scope uniqueness to this class, you
# should use the class name as part of the unique id.
def unique_id method = nil, &block
if method
define_method :set_unique_id do
self['_id'] ||= self.send(method)
end
elsif block
define_method :set_unique_id do
uniqid = block.call(self)
raise ArgumentError, "unique_id block must not return nil" if uniqid.nil?
self['_id'] ||= uniqid
end
end
end
# Define a CouchDB view. The name of the view will be the concatenation
# of <tt>by</tt> and the keys joined by <tt>_and_</tt>
#
# ==== Example views:
#
# class Post
# # view with default options
# # query with Post.by_date
# view_by :date, :descending => true
#
# # view with compound sort-keys
# # query with Post.by_user_id_and_date
# view_by :user_id, :date
#
# # view with custom map/reduce functions
# # query with Post.by_tags :reduce => true
# view_by :tags,
# :map =>
# "function(doc) {
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# if (doc['couchrest-type'] == 'Post' && doc.tags) {
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# doc.tags.forEach(function(tag){
# emit(doc.tag, 1);
# });
# }
# }",
# :reduce =>
# "function(keys, values, rereduce) {
# return sum(values);
# }"
# end
#
# <tt>view_by :date</tt> will create a view defined by this Javascript
# function:
#
# function(doc) {
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# if (doc['couchrest-type'] == 'Post' && doc.date) {
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# emit(doc.date, null);
# }
# }
#
# It can be queried by calling <tt>Post.by_date</tt> which accepts all
# valid options for CouchRest::Database#view. In addition, calling with
# the <tt>:raw => true</tt> option will return the view rows
# themselves. By default <tt>Post.by_date</tt> will return the
# documents included in the generated view.
#
# CouchRest::Database#view options can be applied at view definition
# time as defaults, and they will be curried and used at view query
# time. Or they can be overridden at query time.
#
# Custom views can be queried with <tt>:reduce => true</tt> to return
# reduce results. The default for custom views is to query with
# <tt>:reduce => false</tt>.
#
# Views are generated (on a per-model basis) lazily on first-access.
# This means that if you are deploying changes to a view, the views for
# that model won't be available until generation is complete. This can
# take some time with large databases. Strategies are in the works.
#
# To understand the capabilities of this view system more compeletly,
# it is recommended that you read the RSpec file at
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# <tt>spec/core/model_spec.rb</tt>.
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def view_by *keys
opts = keys.pop if keys.last.is_a?(Hash)
opts ||= {}
type = self.to_s
method_name = "by_#{keys.join('_and_')}"
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self.generated_design_doc ||= default_design_doc
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ducktype = opts.delete(:ducktype)
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if opts[:map]
view = {}
view['map'] = opts.delete(:map)
if opts[:reduce]
view['reduce'] = opts.delete(:reduce)
opts[:reduce] = false
end
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generated_design_doc['views'][method_name] = view
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else
doc_keys = keys.collect{|k|"doc['#{k}']"}
key_protection = doc_keys.join(' && ')
key_emit = doc_keys.length == 1 ? "#{doc_keys.first}" : "[#{doc_keys.join(', ')}]"
map_function = <<-JAVASCRIPT
function(doc) {
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if (#{!ducktype ? "doc['couchrest-type'] == '#{type}' && " : ""}#{key_protection}) {
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emit(#{key_emit}, null);
}
}
JAVASCRIPT
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generated_design_doc['views'][method_name] = {
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'map' => map_function
}
end
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generated_design_doc['views'][method_name]['couchrest-defaults'] = opts
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self.design_doc_fresh = false
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method_name
end
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def method_missing m, *args
if opts = has_view?(m)
query = args.shift || {}
view(m, opts.merge(query), *args)
else
super
end
end
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# returns stored defaults if the there is a view named this in the design doc
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def has_view?(view)
view = view.to_s
if generated_design_doc['views'][view]
generated_design_doc['views'][view]["couchrest-defaults"]
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end
end
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# Fetch the generated design doc. Could raise an error if the generated views have not been queried yet.
def design_doc
database.get("_design/#{design_doc_slug}")
end
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# Dispatches to any named view.
def view name, query={}, &block
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unless design_doc_fresh
refresh_design_doc
end
query[:raw] = true if query[:reduce]
raw = query.delete(:raw)
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view_name = "#{design_doc_slug}/#{name}"
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fetch_view_with_docs(view_name, query, raw, &block)
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end
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private
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def fetch_view_with_docs name, opts, raw=false, &block
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if raw
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fetch_view name, opts, &block
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else
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begin
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view = fetch_view name, opts.merge({:include_docs => true}), &block
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view['rows'].collect{|r|new(r['doc'])} if view['rows']
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rescue
# fallback for old versions of couchdb that don't
# have include_docs support
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view = fetch_view name, opts, &block
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view['rows'].collect{|r|new(database.get(r['id']))} if view['rows']
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end
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end
end
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def fetch_view view_name, opts, &block
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retryable = true
begin
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database.view(view_name, opts, &block)
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# the design doc could have been deleted by a rouge process
rescue RestClient::ResourceNotFound => e
if retryable
refresh_design_doc
retryable = false
retry
else
raise e
end
end
end
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def design_doc_slug
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return design_doc_slug_cache if design_doc_slug_cache && design_doc_fresh
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funcs = []
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generated_design_doc['views'].each do |name, view|
funcs << "#{name}/#{view['map']}#{view['reduce']}"
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end
md5 = Digest::MD5.hexdigest(funcs.sort.join(''))
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self.design_doc_slug_cache = "#{self.to_s}-#{md5}"
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end
def default_design_doc
{
"language" => "javascript",
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"views" => {
'all' => {
'map' => "function(doc) {
if (doc['couchrest-type'] == '#{self.to_s}') {
emit(null,null);
}
}"
}
}
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}
end
def refresh_design_doc
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did = "_design/#{design_doc_slug}"
saved = database.get(did) rescue nil
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if saved
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generated_design_doc['views'].each do |name, view|
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saved['views'][name] = view
end
database.save(saved)
else
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generated_design_doc['_id'] = did
database.save(generated_design_doc)
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end
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self.design_doc_fresh = true
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end
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end # class << self
# returns the database used by this model's class
def database
self.class.database
end
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# alias for self['_id']
def id
self['_id']
end
# alias for self['_rev']
def rev
self['_rev']
end
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# Takes a hash as argument, and applies the values by using writer methods
# for each key. Raises a NoMethodError if the corresponding methods are
# missing. In case of error, no attributes are changed.
def update_attributes hash
hash.each do |k, v|
raise NoMethodError, "#{k}= method not available, use key_accessor or key_writer :#{k}" unless self.respond_to?("#{k}=")
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end
hash.each do |k, v|
self.send("#{k}=",v)
end
save
end
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# returns true if the document has never been saved
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def new_record?
!rev
end
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# Saves the document to the db using create or update. Also runs the :save
# callbacks. Sets the <tt>_id</tt> and <tt>_rev</tt> fields based on
# CouchDB's response.
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def save
if new_record?
create
else
update
end
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end
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# Deletes the document from the database. Runs the :delete callbacks.
# Removes the <tt>_id</tt> and <tt>_rev</tt> fields, preparing the
# document to be saved to a new <tt>_id</tt>.
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def destroy
result = database.delete self
if result['ok']
self['_rev'] = nil
self['_id'] = nil
end
result['ok']
end
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protected
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# Saves a document for the first time, after running the before(:create)
# callbacks, and applying the unique_id.
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def create
set_unique_id if respond_to?(:set_unique_id) # hack
save_doc
end
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# Saves the document and runs the :update callbacks.
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def update
save_doc
end
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private
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def save_doc
result = database.save self
if result['ok']
self['_id'] = result['id']
self['_rev'] = result['rev']
end
result['ok']
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end
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def apply_defaults
if self.class.default
self.class.default.each do |k,v|
self[k.to_s] = v
end
end
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end
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def cast_keys
return unless self.class.casts
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# TODO move the argument checking to the cast method for early crashes
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self.class.casts.each do |k,v|
next unless self[k]
target = v[:as]
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if target.is_a?(Array)
klass = ::Extlib::Inflection.constantize(target[0])
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self[k] = self[k].collect do |value|
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klass.new(value)
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end
else
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self[k] = ::Extlib::Inflection.constantize(target).new(self[k])
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end
end
end
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include ::Extlib::Hook
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register_instance_hooks :save, :create, :update, :destroy
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end # class Model
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end # module CouchRest