347 lines
11 KiB
Ruby
347 lines
11 KiB
Ruby
module CouchRest
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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::MagicViews#view_by for documentation about the view-generation system. For the other class methods, inspiried by DataMapper and ActiveRecord, see CouchRest::Model::ClassMethods. The InstanceMethods are pretty basic.
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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
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# include 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.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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# doc['slug'] = title.downcase.gsub(/[^a-z0-9]/,'-').squeeze('-').gsub(/^\-|\-$/,'')
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# end
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# end
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module Model
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class << self
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# this is the CouchRest::Database that model classes will use unless they override it with <tt>use_database</tt>
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attr_accessor :default_database
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end
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# instance methods on the model classes
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module InstanceMethods
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attr_accessor :doc
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def initialize keys = {}
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self.doc = {}
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keys.each do |k,v|
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doc[k.to_s] = v
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end
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unless doc['_id'] && doc['_rev']
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init_doc
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end
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end
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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 doc['_id']
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def id
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doc['_id']
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end
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# alias for doc['_rev']
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def rev
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doc['_rev']
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end
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# returns true if the doc has never been saved
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def new_record?
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!doc['_rev']
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end
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# save the doc to the db using create or update
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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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protected
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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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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 doc
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if result['ok']
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doc['_id'] = result['id']
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doc['_rev'] = result['rev']
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end
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result['ok']
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end
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def init_doc
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doc['type'] = self.class.to_s
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end
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end # module InstanceMethods
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# these show up as class methods on models that include CouchRest::Model
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module ClassMethods
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# override the CouchRest::Model-wide default_database
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def use_database db
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@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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@database || CouchRest::Model.default_database
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end
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# load a document from the database
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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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# Defines methods for reading and writing from fields in the document. 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 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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doc[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 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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doc[key]
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end
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end
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end
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# 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
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def timestamps!
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before(:create) do
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doc['updated_at'] = doc['created_at'] = Time.now
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end
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before(:update) do
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doc['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, 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.
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def unique_id method
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define_method :set_unique_id do
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doc['_id'] ||= self.send(method)
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end
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end
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end # module ClassMethods
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module MagicViews
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# 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>
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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.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 function:
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#
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# function(doc) {
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# if (doc.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 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.
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#
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# 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.
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#
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# 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>.
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#
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# To understand the capabilities of this view system more compeletly, it is recommended that you read the RSpec file at <tt>spec/core/model.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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@@design_doc ||= default_design_doc
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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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@@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 (doc.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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@@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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@@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 = "#{type}/#{method_name}"
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view = fetch_view(view_name, query)
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if raw
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view
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else
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# TODO this can be optimized once the include-docs patch is applied
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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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end
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private
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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_id
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"_design/#{self.to_s}"
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end
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def default_design_doc
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{
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"_id" => design_doc_id,
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"language" => "javascript",
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"views" => {}
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}
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end
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def refresh_design_doc
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saved = database.get(design_doc_id) rescue nil
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if saved
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@@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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database.save(@@design_doc)
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end
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@@design_doc_fresh = true
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end
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end # module MagicViews
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module Callbacks
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def self.included(model)
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model.class_eval <<-EOS, __FILE__, __LINE__
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include Extlib::Hook
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register_instance_hooks :save, :create, :update #, :destroy
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EOS
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end
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end # module Callbacks
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# bookkeeping section
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# load the code into the model class
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def self.included(model)
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model.send(:include, InstanceMethods)
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model.extend ClassMethods
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model.extend MagicViews
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model.send(:include, Callbacks)
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end
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end # module Model
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end # module CouchRest |