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