Can nested attributes be used in combination with inheritance?

Question

I have the following classes:

Project
Person
Person > Developer
Person > Manager

In the Project model I have added the following statements:

has_and_belongs_to_many :people
accepts_nested_attributes_for :people

And of course the appropriate statements in the class Person. How can I add a Developer to a Project through the nested_attributes method? The following does not work:

@p.people_attributes = [{:name => "Epic Beard Man", :type => "Developer"}]
@p.people
=> [#<Person id: nil, name: "Epic Beard Man", type: nil>]

As you can see the type attributes is set to nil instead of "Developer".

tokland · Answer 1 · 2012-10-11T16:39:09.993

7

Solution for Rails3: attributes_protected_by_default in now a class-method:

class Person < ActiveRecord::Base

  private

  def self.attributes_protected_by_default
    super - [inheritance_column]
  end
end

edited Oct 11 '12 at 16:39

answered Jul 04 '12 at 09:00

tokland

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Note: Make sure you put this near the top of the class, *before* any calls to `attr_protected`. The first call to `attr_protected` will cause it to call whatever version of `attributes_protected_by_default` is currently defined, which will be the default version from AR unless you've overridden it by that point... – Tyler Rick Nov 28 '14 at 18:31

score 5 · Accepted Answer · edited May 23 '17 at 09:57

5

I encountered a similar problem few days ago. The inheritance column(i.e. type) in a STI model is a protected attribute. Do the following to override the default protection in your Person class.

Rails 2.3

class Person < ActiveRecord::Base

private
  def attributes_protected_by_default
    super - [self.class.inheritance_column]
  end
end

Rails 3

Refer to the solution suggested by @tokland.

Caveat:

You are overriding the system protected attribute.

Reference:

SO Question on the topic

edited May 23 '17 at 09:57

Community

1
1

answered Mar 31 '10 at 18:58

Harish Shetty

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note: this works for Rails 2.3, see my answer below for Rails 3 – tokland Jul 04 '12 at 08:59
@tokland, I hadn't visited this question for sometime. I have updated my answer with a Rails 3 solution. – Harish Shetty Jul 04 '12 at 21:52
great. I'd write a simple `def self.attributes_protected_by_default`, but whatever. – tokland Jul 04 '12 at 22:05
@tokland, you are right over-riding the class method is easier. When I was testing that approach, as I had a funky object/class state in my irb session and the `super` call didn't work. – Harish Shetty Jul 04 '12 at 22:28

score 4 · Answer 3 · answered Jun 03 '10 at 20:22

4

Patches above did not work for me, but this did (Rails3):

class ActiveRecord::Reflection::AssociationReflection
  def build_association(*options)
    if options.first.is_a?(Hash) and options.first[:type].presence
      options.first[:type].to_s.constantize.new(*options)
    else
      klass.new(*options)
    end
  end
end

Foo.bars.build(:type=>'Baz').class == Baz

answered Jun 03 '10 at 20:22

grosser

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This solution works for associations, but not for stand along STI object construction. I have updated my answer with a generic Rails 3 solution. – Harish Shetty Jul 04 '12 at 21:54

score 0 · Answer 4 · answered Jun 29 '13 at 03:27

0

For those of us using Mongoid, you will need to make the _type field accessible:

class Person
  include Mongoid::Document
  attr_accessible :_type
end

answered Jun 29 '13 at 03:27

Andrew

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Can nested attributes be used in combination with inheritance?

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