Nested attributes for best practices

Question

I have a model has nested attributes with another.

My question is: how better solution for call a build in controller or model?

See that model:

class ContentType < ActiveRecord::Base
  after_initialize :add_fields
  belongs_to :project
  has_many :field_content_types

  accepts_nested_attributes_for :field_content_types, reject_if: proc {|attributes| attributes['name'].blank?}

  private

  def add_fields
    self.field_content_types.build if new_record?
  end
end

Either remove after_initialize in model and add line in controller

class ContentTypesController < ApplicationController
  def new
    @content_type = ContentType.new
    @content_type.field_content_types.build
  end
end

Have one reason to set build in controller?

Answer 1

Assuming you are asking where you should build field_content_types, in this particular case, I don't think it matters whether you build it in model or controller.

The rule of thumb is to keep the controller thin and model fat, but the build method already so concise that you won't gain much from building it from model.

Personally, I would just build it in the controller.