Our Rails application needs to support both xml and json formats. In some cases, we need to return custom XML that spans several objects and associations. I've been able to write custom to_xml methods that use the builder and block functionality. When trying the same thing with the to_json method, I failed to get the same result.
Basically to_xml has this signature: to_xml(options = {}, &block). I've perused around and it appears to_json has this signature: to_json(options = {}). Is there a version of to_json that will yield to a block and provide the json builder? Can someone please tell me if I've done something wrong with the code below? Is there is a plugin or newer version of Rails that will add the same support for to_json that to_xml supports?
Here is the relevant code
class Conference < ActiveRecord::Base has_many :courses, :dependent => :destroy end
class Course < ActiveRecord::Base belongs_to :conference has_many :sessions, :dependent => :destroy has_one :manual
# just a place holder method so we can serialize it def pre_requisite "An open mind" end end
class Session < ActiveRecord::Base belongs_to :courses has_one :presentation, :dependent=>:destroy
# just a place holder method so we can serialize it def maximum_capacity_reached? false; end end
class Presentation < ActiveRecord::Base belongs_to :session belongs_to :instructor end
class Manual < ActiveRecord::Base belongs_to :course end
class Instructor < ActiveRecord::Base end
Now let's suppose I have a controller that will return the full detail of a conference and needs all of the related data and will also serialize some custom methods. class ConferencesController < ApplicationController # GET /conferences/:id def show conference_id = params[:id]
respond_to do |format| format.html # unsupported format.json { render(:json=>Conference.full_json(conference_id)) } format.xml { render(:xml=>Conference.full_xml(conference_id)) } end end end
So I've extended the conference class so that it can build this nested xml along with the result of selective methods on various classes. this code uses the fact that to_xml has this signature: to_xml(options = {}, &block)
class Conference < ActiveRecord::Base has_many :courses, :dependent => :destroy
def slogan "#{name}: Be here or be in the dark!" end
def self.full_xml(conference_id) # ensure we've loaded the full structure in the most efficient manner conference = Conference.find(conference_id, :include=>{:courses => [:manual, {:sessions=>:presentation}]})
# extract detailed hierarchical xml conference.to_xml do |xml| xml.slogan conference.slogan # output the banner
#iterate courses and any custom methods xml.courses{ conference.courses.each do |course| course.to_xml(:builder=>xml, :skip_instruct => true) do | xml_course| xml_course.sessions{ #iterate sessions and any custom methods course.sessions.each do |session| session.to_xml(:builder=>xml_course, :skip_instruct => true) do |xml_course_session| xml_course_session.is_at_capacity session.maximum_capacity_reached? end end } end end } end end
def self.full_json(conference_id) # ensure we've loaded the full structure in the most efficient manner conference = Conference.find(conference_id, :include=>{:courses => [:manual, {:sessions=>:presentation}]})
debugger()
# extract detailed hierarchical xml conference.to_json do |json| json.slogan conference.slogan # output the banner
#iterate courses and any custom methods json.courses{ conference.courses.each do |course| course.to_json(:builder=>json, :skip_instruct => true) do | json_course| json_course.sessions{ #iterate sessions and any custom methods course.sessions.each do |session| session.to_json(:builder=>json_course, :skip_instruct => true) do |json_course_session| json_course_session.is_at_capacity session.maximum_capacity_reached? end end } end end } end end end
When I invoke the method, via http://localhost:3000/conferences/1.xml, I get the desired generated XML output: <conference> <created-at type="datetime">2008-11-04T13:59:41-08:00</created-at> <id type="integer">1</id> <name>Ruby Live</name> <updated-at type="datetime">2008-11-04T13:59:41-08:00</updated-at> <slogan>Ruby Live: Be here or be in the dark!</slogan>