Global Settings for storing app configuration(with caching)

boolean_value.rb

class BooleanValue < Value
end

create_settings_migration.rb

class CreateSettings < ActiveRecord::Migration
  def change
		create_table :settings do |t|
			t.string :name
			t.timestamps
		end
		
		create_table :value_associations do |t|
			t.integer :setting_id
			t.integer :value_id
			t.string 	:value_type
		end
		
		create_table :string_values do |t|
			t.string :value
			t.timestamps
		end
		
		create_table :integer_values do |t|
			t.integer :value
			t.timestamps
		end
		
		create_table :float_values do |t|
			t.float :value
			t.timestamps
		end
		
		create_table :boolean_values do |t|
			t.boolean :value
			t.timestamps
		end
  end
end

float_value.rb

class FloatValue < Value
end

integer_value.rb

class IntegerValue < Value
end

setting_spec.rb

require 'spec_helper'

describe Setting do
  subject { Setting.new }

  [:name, :value].each do |propery|
    it { should respond_to propery }
  end
  it { should validate_uniqueness_of :name }

  describe Setting, 'class methods' do
    subject { Setting }

    [:write, :read, :remove, :remove_all].each do |m|
      it { should respond_to m }
    end
  end

end

settings.rb

class Setting < ActiveRecord::Base
  has_one :value_association, :dependent => :destroy

  validates :name, uniqueness: true, presence: true

  after_commit :flush_cache

  def self.write(name, value)
    setting = find_or_initialize_by_name(name)
    setting.update_attribute(:value, value)
  end

  def self.read(name)
    Rails.cache.fetch([name]) { find_by_name!(name).value.value }
  end

  def self.remove(name)
    find_by_name!(name).destroy
  end

  def self.remove_all
    destroy_all
  end

  def value
    value_association.value
  end

  def value=(new_value)
    if self.value_association
      self.value_association.destroy
      flush_cache
    end
    self.value_association = ValueAssociation.new(value: Value.new_value(new_value))
  end

  private

  def flush_cache
    Rails.cache.delete([name])
  end

end

shared_examples_for_value.rb

shared_examples_for 'value' do
  it { should respond_to :value }

  it { should have_one :setting }
  it { should have_one :value_association }
end

string_value.rb

class StringValue < Value
end

value.rb

class Value < ActiveRecord::Base
	self.abstract_class = true

	has_one :value_association, as: :value
	has_one :setting, through: :value_association
	
	attr_accessible :value
	
	def self.new_value(value)
		case value
	  when String then StringValue.new(value: value)
	  when Integer then IntegerValue.new(value: value)
	  when Float then FloatValue.new(value: value)
	  when TrueClass, FalseClass then BooleanValue.new(value: value)
	  else
	    raise TypeError, "Cannot find type for #{value}"
	  end
	end
end

value_association.rb

class ValueAssociation < ActiveRecord::Base
	belongs_to :setting
	belongs_to :value, :polymorphic => true, :dependent => :destroy
	
	attr_accessible :setting, :value
end

value_spec.rb

require 'spec_helper'

describe StringValue do
  subject { StringValue.new }

  it_behaves_like 'value'
end

describe IntegerValue do
  subject { IntegerValue.new }

  it_behaves_like 'value'
end

describe FloatValue do
  subject { FloatValue.new }

  it_behaves_like 'value'
end

describe BooleanValue do
  subject { BooleanValue.new }

  it_behaves_like 'value'
end