Reform 1.2.6 nested form (with support for cocoon gem)

graduation_form.rb

# app/forms/graduation_form.rb

require 'concerns/nested_form'

class GraduationForm < Reform::Form
  # Needed for correct behavior of virtual attributes, see https://github.com/apotonick/reform/issues/75
  reform_2_0!

  model :response

  collection :minor_responses, populate_if_empty: MinorResponse do
    include Reform::NestedForm
    property :minor_name
    
    # only save this if minor_name isn't blank
    reject_if_blank :minor_name
  end

end

nested_form.rb

# app/forms/concerns/nested_form.rb

# Helps facilitates nested forms. loosely based on: https://github.com/apotonick/reform/issues/86#issuecomment-73918238
# Adds the ability to exclude saving if a particular field is blank, and helper methods to make cocoon gem work.

module Reform
  module NestedForm
    extend ActiveSupport::Concern

    included do
      property :id, virtual: true
      property :_destroy, virtual: true
      @reject_field = []
    end

    def sync_hash(options)
      if fields._destroy == '1' || reject_fields?
        model.mark_for_destruction
      end
      super(options)
    end

    def new_record?
      model.new_record?
    end

    def marked_for_destruction?
      model.marked_for_destruction?
    end

    def reject_fields?
      self.class.reject_field.any? { |f| fields[f].blank? }
    end

    class_methods do
      def reject_if_blank(field)
        @reject_field << field
      end

      def reject_field
        @reject_field
      end
    end

  end
end

response.rb

# app/models/response.rb

class Response < ActiveRecord::Base
  # autosave: true is needed to get mark_for_destruction
  has_many :minor_responses, dependent: :destroy, autosave: true
end

@bkildow thanks for this just started refactoring an App that makes heavy use of cocoon to include reform - How Cocoon and reform would interact concerned me but evidently it is do able

@bkildow This worked for me with Trailblazer contracts, although I was getting undefined method 'build' for #<Disposable::Twin::Collection:...>

I found a workaround by overriding Cocoon::ViewHelpers#create_object_on_association. It expects the form collection to be ActiveRecord, with a build method, but Disposable::Twin::Collection doesn't have build. So I ask the model for the raw collection's buildinstead.

# via https://github.com/nathanvda/cocoon/blob/be59abd99027b0cce25dc4246c86d60b51c5e6f2/lib/cocoon/view_helpers.rb#L133-L136
module Cocoon
  module ViewHelpers
    def create_object_on_association(f, association, instance, force_non_association_create)
      if instance.class.name == "Mongoid::Relations::Metadata" || force_non_association_create
        create_object_with_conditions(instance)
      else
        assoc_obj = nil

        if instance.collection?

          if f.object.respond_to?(:model) && f.object.send(association).is_a?(Disposable::Twin::Collection)
            # HACK! Add Disposable::Twin::Collection support
            assoc_obj = f.object.model.send(association).build
            f.object.model.send(association).delete(assoc_obj)

          else
            # assume ActiveRecord or compatible
            assoc_obj = f.object.send(association).build
            f.object.send(association).delete(assoc_obj)
          end
        else
          assoc_obj = f.object.send("build_#{association}")
          f.object.send(association).delete
        end

        assoc_obj = assoc_obj.dup if assoc_obj.frozen?

        assoc_obj
      end
    end
  end
end

Also, if you get undefined method 'reflect_on_association', be sure in your contract you include Reform::Form::ActiveModel::ModelReflections.

One more Trailblazer note: sync_hash is no longer part of the Reform API. So I commented out sync_hash and instead followed the instructions in the Trailblazer book re: "Removing Collection Items".

So the collection's skip_if looks like:

def skip_item?(fragment, options)
  # don't process if it's getting destroyed!
  if fragment["_destroy"] == "1"
    items.delete(item.find { |x| x.id.to_s == fragment["id"] })
    return true
  end
end

Here is an update that works with Reform 2.2.1:

https://gist.github.com/lucaspiller/615f09bb525a14163921fd56b4b8e611