Rails 3 - Building forms from Serialized Data - serialization

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

I suggest you have a look at something like attr_bucket. Ostensibly, this can be used to solve some inheritance annoyances, but it will also solve your problem for you. Here is the essence.
It looks like you know what all your permissions are, but you want to serialize all of them into the same database field. But within your actual rails app, you want to treat all your permissions as if they were totally separate fields. This is exactly what a solution like attr_bucket will let you do. Let's take your example, you would do something like this:
class User::Affiliation::Role < ActiveRecord::Base
attr_bucket :permissions => [:permissions_customer_club_events_read, :permissions_customer_club_events_write, :permission_do_crazy_things]
after_initialize :init
def init
## Sets base permission structure ##
self.permissions ||= YAML.load_file("#{Rails.root}/config/permissions.yml")
end
end
Now you will be able to use permissions_customer_club_events_read, permissions_customer_club_events_write, permission_do_crazy_things as if they were separate database fields (this includes using them in forms etc.), but when you actually save your objects all those fields would get 'bucketed' together and serialized into the :permissions field.
The only caveat is the serialization mechanism, I believe attr_bucket will serialize everything using YAML, whereas you were using JSON. If this doesn't matter then you're golden, otherwise you might need to patch attr_bucket to use json instead of YAML which should be pretty straight forward.

Answer 2

Sorry if I did not understand the question ;)
You could have a customdata module, included in your model, and use method_missing:
module CustomData
def self.included(base)
base.instance_eval do
after_save :save_data
end
def method_missing(method, *args, &block)
if method.to_s =~ /^data_/
data[method] ? data[method] : nil
else
super
end
end
def data
#data ||= begin
#get and return your data
end
end
private
def save_data
end
end
With this method, you would have to use f.check_box :data_permissions_customer_club_events_read
It's not really complete, but I hope you get the idea ;)
attr_bucket seems like a good solution too.

Answer 3

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.