This plugin allows attaching arbitrary set of attributes to a model, with inheritance. It is modeled after OpenStruct, for example:

user = User.create
user.settings.language = 'en'
user.settings.site_theme = 'green'
user.settings.is_sidebar_hidden = true

etc.

script/plugin install git:https://github.com/invisiblellama/has_settings.git

Suppose you have global application-wide set of preferences and you want to be able to override some of these preferences for selected users or user groups.

class Setting < ActiveRecord::Base
  acts_as_setting
end

The structure of settings table is as follows:

create_table :settings do |t|
  t.integer :configurable_id
  t.string  :configurable_type
  t.string  :name, :limit => 40, :null => false
  t.string  :value
  t.string  :value_type
end

This gives you access to global settings store:

Setting.global.some_setting = 42
Setting.global.some_other_setting = true

global is the default name of global settings accessor added by acts_as_setting to model, you can give it different name by passing parameter to acts_as_setting, f.i.:

acts_as_setting :general

Group model, inherits global settings from Setting

class Group < ActiveRecord::Base
  has_many :users
  has_settings :settings, :inherit => Setting
end

User, inheriting from Group

class User < ActiveRecord::Base
  belongs_to :group
  has_settings :settings, :inherit => :group
end

# set global 'site_theme'
Setting.global.site_theme = 'default'
Setting.global.site_theme
# => 'default'

# Group doesn't have 'site_theme' but it inherits from global settings, so
group.settings.site_theme
# => 'default'

# so does User
user.settings.site_theme
# => 'default'

# override 'site_theme' for the Group
group.settings.site_theme = 'green'
group.settings.site_theme
# => 'green'
# User inherits from the Group, so
user.settings.site_theme
# => 'green'

# set 'site_theme' to nil to delete it
group.settings.site_theme = nil
# now both User and Group see global setting again
user.settings.site_theme
# => 'default'
group.settings.site_theme
# => 'default'

The interface is intentionally minimal. Assigning value to (almost arbitrary) named attribute will create named setting, assigning nil will delete it. Only simple types are supported:

• boolean values (TrueClass, FalseClass)

• String

• Float

• Fixnum and Bignum

• Time, Date, DateTime and ActiveSupport::TimeWithZone

Additionally, settings proxy provides a few public methods:

has_setting?(symbol_or_name, include_inherited = true)

will check if setting symbol_or_name is defined for the settings owner;

all(include_inherited = true)

will return all defined settings as a Hash. If include_inherited is set to false, only settings defined for the receiver will be checked and inheritance ignored.

And finally, key-value syntax is also supported:

group.settings['site_theme']              # same as group.settings.site_theme
group.settings[:site_theme] = 'ponies'    # same as group.settings.site_theme = 'ponies'

Copyright © 2009 Dmitri Goutnik, released under the MIT license.