Question

I can’t seem to figure out how to update or destroy EmbeddedDocuments in MongoMapper. Through Googling I’ve seen different methods like delete_if {} and others, but none seem to work for me semantically. Is there anything built-in to MongoMapper to help with this?

class Schedule
  include MongoMapper::Document

  key :name, String
  key :description, String
  key :active, Boolean, :default => false

  many :periods

  validates_presence_of :name

  def activate!
    set({:active => true}, :active => false)

    self.active = true
  end
end

class Period
  include MongoMapper::EmbeddedDocument

  key :number, Integer
  key :text, String
  key :start, Time
  key :finish, Time

  embedded_in :schedule

  before_validation :number!

  validates_presence_of :number
  validates_presence_of :text
  validates_presence_of :start
  validates_presence_of :finish

  validates_format_of :start, :with => /^(2[0-3]|[01]?[0-9]):([0-5]?[0-9])$/
  validates_format_of :finish, :with => /^(2[0-3]|[01]?[0-9]):([0-5]?[0-9])$/

  def number!
    unless self.number
      number = schedule.periods.count + 1
    end
  end
end

Answer 1

The follow test shows examples on how to update and remove embedded documents in two ways:
(1) via Ruby using standard Array accessors and methods, and
(2) via Mongo (MongoMapper / MongoDB) for update and removal of embedded documents on the DB server

References:

http://www.ruby-doc.org/core-1.9.3/Array.html#method-i-delete_if
http://mongomapper.com/documentation/plugins/modifiers.html#set
http://www.mongodb.org/display/DOCS/Updating#Updating-%24set

Note that Hash keys containing ‘.’ require use of the old ( => ) syntax. Hope that this helps.

test/unit/period_test.rb

require 'test_helper'

def ppp(obj)
  puts obj.inspect.gsub(/(, |\[)#/, "\\1\n #")
end

class PeriodTest < ActiveSupport::TestCase
  def setup
    Schedule.delete_all
    @today = Time.now.midnight
  end

  test "update and remove embedded documents" do
    schedule = Schedule.create(name: 'George')
    assert_equal(1, Schedule.count)
    schedule.periods << Period.new(number: 1, text: 'period 1', start: @today + 8.hours, finish: @today + 9.hours)
    schedule.periods << Period.new(number: 2, text: 'period 2', start: @today + 9.hours, finish: @today + 10.hours)
    schedule.periods << Period.new(number: 3, text: 'period 3', start: @today + 10.hours, finish: @today + 11.hours)
    schedule.periods.last.finish = @today + 12.hours #update in Ruby
    schedule.save
    assert_equal(1, Schedule.count)
    puts "schedule with three periods --------"
    ppp Schedule.first
    schedule.periods.delete_if {|period| period.text == 'period 2'} #remove in Ruby
    schedule.save
    puts "schedule after removing period 2 in Ruby --------"
    ppp Schedule.first
    Schedule.set( {name: 'George', 'periods.text' => 'period 1'}, {'periods.$.finish' => @today + 10.hours} ) #update embedded document in MongoDB
    puts "schedule after updatting period 1 via Mongo --------"
    ppp Schedule.first
    Schedule.pull( {name: 'George'}, { periods: { text: 'period 1'} } ) #remove embedded document in MongoDB
    puts "schedule after pulling period 1 via Mongo --------"
    ppp Schedule.first
  end
end

output

Run options: --name=test_update_and_remove_embedded_documents

# Running tests:

schedule with three periods --------
#<Schedule _id: BSON::ObjectId('4ff732e77f11ba6fe9000001'), active: false, name: "George", periods: [
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000002'), finish: Fri, 06 Jul 2012 13:00:00 UTC +00:00, number: 1, start: Fri, 06 Jul 2012 12:00:00 UTC +00:00, text: "period 1">,
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000003'), finish: Fri, 06 Jul 2012 14:00:00 UTC +00:00, number: 2, start: Fri, 06 Jul 2012 13:00:00 UTC +00:00, text: "period 2">,
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000004'), finish: Fri, 06 Jul 2012 16:00:00 UTC +00:00, number: 3, start: Fri, 06 Jul 2012 14:00:00 UTC +00:00, text: "period 3">]>
schedule after removing period 2 in Ruby --------
#<Schedule _id: BSON::ObjectId('4ff732e77f11ba6fe9000001'), active: false, name: "George", periods: [
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000002'), finish: Fri, 06 Jul 2012 13:00:00 UTC +00:00, number: 1, start: Fri, 06 Jul 2012 12:00:00 UTC +00:00, text: "period 1">,
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000004'), finish: Fri, 06 Jul 2012 16:00:00 UTC +00:00, number: 3, start: Fri, 06 Jul 2012 14:00:00 UTC +00:00, text: "period 3">]>
schedule after updatting period 1 via Mongo --------
#<Schedule _id: BSON::ObjectId('4ff732e77f11ba6fe9000001'), active: false, name: "George", periods: [
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000002'), finish: Fri, 06 Jul 2012 14:00:00 UTC +00:00, number: 1, start: Fri, 06 Jul 2012 12:00:00 UTC +00:00, text: "period 1">,
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000004'), finish: Fri, 06 Jul 2012 16:00:00 UTC +00:00, number: 3, start: Fri, 06 Jul 2012 14:00:00 UTC +00:00, text: "period 3">]>
schedule after pulling period 1 via Mongo --------
#<Schedule _id: BSON::ObjectId('4ff732e77f11ba6fe9000001'), active: false, name: "George", periods: [
 #<Period _id: BSON::ObjectId('4ff732e77f11ba6fe9000004'), finish: Fri, 06 Jul 2012 16:00:00 UTC +00:00, number: 3, start: Fri, 06 Jul 2012 14:00:00 UTC +00:00, text: "period 3">]>
.

Finished tests in 0.038952s, 25.6726 tests/s, 51.3452 assertions/s.

1 tests, 2 assertions, 0 failures, 0 errors, 0 skips