Question

I’ve been working on a rails project where I am needed to serialize permissions for user roles and store in the database. As far as that goes I’m all good. Now my problem comes when I want to modify the serialized data from a rails generated form.

I acted on instinct and tried with the expected behavior.
That would be to use something like this:

f.check_box :permissions_customer_club_events_read

But as no getters or setters exist for the serialized data, this doesn’t work (obviously :p). Now I wonder how I would go about tackling this problem and the only thing that comes to mind is dynamically generating getter and setter methods from my serialized hash.

Example:

def permissions_customer_club_events_read=(val)
  permissions[:customer][:club][:events][:read] = val
end

def permissions_customer_club_events_read
  permissions[:customer][:club][:events][:read]
end

Anyone understand what I’m getting at?

Here is my Model:

class User::Affiliation::Role < ActiveRecord::Base
  require 'yajl'

  class YajlCoder
    def dump data
      Yajl.dump data
    end
    def load data
      return unless data
      Yajl.load data
    end
  end

  serialize :permissions, YajlCoder.new

  after_initialize :init

  def init
    ## Sets base permission structure ##
    self.permissions ||= YAML.load_file("#{Rails.root}/config/permissions.yml")
  end

end

Answer 1

This worked out for me in the end, this is how I solved it.

---

serialize :permissions, YajlCoder.new

after_initialize :init

def init
  self.permissions ||= YAML.load_file("#{Rails.root}/config/permissions.yml")['customer']
  build_attributes_from self.permissions, :permissions
end

private

def build_attributes_from store, prefix, path=[]
  store.each do |k,v|
    if v.class == Hash
      build_attributes_from v, prefix, ( path + [k] )
    else
      create_attr_accessors_from prefix, ( path + [k] )
    end
  end
end

def create_attr_accessors_from prefix, path=[]
  method_name = prefix.to_s + "_" + path.join('_')
  class << self
    self
  end.send :define_method, method_name do
    self.permissions.dig(:path => path)
  end
  class << self
    self
  end.send :define_method, "#{method_name}=" do |value|
    self.permissions.dig(:path => path, :value => value)
  end
end

And some monkey patching for hashes…

class Hash
  def dig(args={})

    path  = args[:path].to_enum   ||  []
    value = args[:value]          ||  nil

    if value == nil
      path.inject(self) do |location, key|
        location.respond_to?(:keys) ? location[key] : nil
      end
    else
      path.inject(self) do |location, key|
        location[key] = ( location[key].class == Hash ) ? location[key] : value
      end
    end
  end
end

Now getter and setter methods are generated for all of the serialized fields.