Question

Model:

class Plan
  include Mongoid::Document
  # Fields
  field :name, type: String

  # Relationships
  references_many :sub_plans,
    :autosave           => true,
    :class_name         => 'Plan',
    :inverse_class_name => 'Plan',
    :inverse_of         => :super_plans
  references_many :super_plans,
    :class_name         => 'Plan',
    :inverse_class_name => 'Plan',
    :inverse_of         => :sub_plans
  accepts_nested_attributes_for :sub_plans

  # Validations
  validates_presence_of :name
end

Test:

describe Plan do
  it "should always have a name" do
    plan = Plan.new
    plan.save.should == false
    plan[:name] = "World Domination"
    plan.save.should == true
  end
  it "should allow nested plan creation" do
    plan = Plan.new(:name => "World Domination", :sub_plans_attributes => {
      :name => "Get $50b",
      :sub_plans_attributes => {
        :name => "Invent"
      }
    });
    plan.sub_plans.count.should == 1
    plan.sub_plans.first.name.should == "Get $50b"
    plan.sub_plans.first.sub_plans.count.should == 1
    plan.sub_plans.first.sub_plans.first.name.should == "Invent"
  end
end

Output with -b:

Running spec/models/plan_spec.rb
.F

Failures:

  1) Plan should allow nested plan creation
     Failure/Error: plan = Plan.new(:name => "World Domination", :sub_plans_attributes => {
     TypeError:
       can't convert Symbol into String
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders/nested_attributes/many.rb:67:in `delete'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders/nested_attributes/many.rb:67:in `destroyable?'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders/nested_attributes/many.rb:103:in `process'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders/nested_attributes/many.rb:30:in `block in build'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders/nested_attributes/many.rb:26:in `each'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders/nested_attributes/many.rb:26:in `build'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/nested_attributes.rb:47:in `block (3 levels) in accepts_nested_attributes_for'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/attributes.rb:193:in `_assigning'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/nested_attributes.rb:45:in `block (2 levels) in accepts_nested_attributes_for'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/attributes/processing.rb:111:in `block in process_nested'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/attributes/processing.rb:110:in `each_pair'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/attributes/processing.rb:110:in `process_nested'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/attributes/processing.rb:122:in `process_pending'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/attributes/processing.rb:29:in `process'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/document.rb:131:in `block in initialize'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/relations/builders.rb:47:in `_building'
     # /usr/lib/ruby/gems/1.9.1/gems/mongoid-2.3.1/lib/mongoid/document.rb:127:in `initialize'
     # ./spec/models/plan_spec.rb:11:in `new'
     # ./spec/models/plan_spec.rb:11:in `block (2 levels) in <top (required)>'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example.rb:48:in `instance_eval'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example.rb:48:in `block in run'
         # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example.rb:107:in `with_around_hooks'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example.rb:45:in `run'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example_group.rb:294:in `block in run_examples'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example_group.rb:290:in `map'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example_group.rb:290:in `run_examples'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/example_group.rb:262:in `run'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/command_line.rb:24:in `block (2 levels) in run'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/command_line.rb:24:in `map'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/command_line.rb:24:in `block in run'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/reporter.rb:12:in `report'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/core/command_line.rb:21:in `run'
     # /usr/lib/ruby/gems/1.9.1/gems/rspec-core-2.6.4/lib/rspec/monkey/spork/test_framework/rspec.rb:5:in `run_tests'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/run_strategy/forking.rb:13:in `block in run'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/forker.rb:21:in `block in initialize'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/forker.rb:18:in `fork'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/forker.rb:18:in `initialize'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/run_strategy/forking.rb:9:in `new'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/run_strategy/forking.rb:9:in `run'
     # /usr/lib/ruby/gems/1.9.1/gems/spork-0.9.0.rc9/lib/spork/server.rb:48:in `run'
     # /usr/lib/ruby/1.9.1/drb/drb.rb:1558:in `perform_without_block'
     # /usr/lib/ruby/1.9.1/drb/drb.rb:1518:in `perform'
     # /usr/lib/ruby/1.9.1/drb/drb.rb:1592:in `block (2 levels) in main_loop'
     # /usr/lib/ruby/1.9.1/drb/drb.rb:1588:in `loop'
     # /usr/lib/ruby/1.9.1/drb/drb.rb:1588:in `block in main_loop'

Finished in 0.00917 seconds
2 examples, 1 failure

Failed examples:

rspec ./spec/models/plan_spec.rb:10 # Plan should allow nested plan creation

Why am I getting this error, and how can I get my many-many self reference working? I’m using Mongoid version 2.3.1 and Rails version 3.1.1. Thanks

Answer 1

After several hours spent trying several different combinations and finally giving up and sleeping on it, I have finally got it to work! Model:

class Plan
  include Mongoid::Document
  # Fields
  field :name, type: String

  # Relationships
  has_and_belongs_to_many :subplans, :inverse_of => :parents,  :class_name => 'Plan', :autosave => true
  has_and_belongs_to_many :parents,  :inverse_of => :subplans, :class_name => 'Plan', :autosave => true
  accepts_nested_attributes_for :subplans

  # Validations
  validates_presence_of :name
end

Tests:

describe Plan do
  it "should always have a name" do
    plan = Plan.new
    plan.save.should == false
    plan[:name] = "World Domination"
    plan.save.should == true
  end
  it "should have a nested relationship" do
    root   = Plan.create          name: "Parent Plan"
    child1 = root.subplans.create name: 'Child Plan #1'
    child2 = Plan.create          name: "Child Plan #2"
    root.subplans << child2

    root.subplans.size.should == 2
    child1.parents.size.should == 1
    child1.parents.first.should == root
    child2.parents.size.should == 1
    child2.parents.first.should == root
  end
  it "should accept nested attributes for subplans" do
    plan = Plan.new :name => "root",
      :subplans_attributes => [{:name => "child"}]
    plan.save; plan.reload
    plan.subplans.size.should == 1
    plan.subplans.first.name.should == "child"
  end
end