preferred

preferred provides a simple mechanism defining and storing preferences on a model. This becomes powerful when used in conjunction with Single Table Inheritance in Rails. Concepts for this gem were initially taken from the Spree open source project and ported to use PostgreSQL JSONB columns instead of separate preferences table.

Usage

To install preferred add the following to your Gemfile

gem 'preferred', git: 'https://github.com/nwwatson/preferred.git'

Once in your Gemfile

bundle install

Simple Example

This simple example shows how to use preferred in a Rails model. Default values are optional. Preferred will provides types for string, decimal, integer, boolean, and date. Preferences are prefixed with "preferred_".

Create a model and ensure that it has a JSONB column called preference_hash

bin/rails g model example_model preference_hash:jsonb

Define preferences in the model and use

class ExampleModel < ApplicationRecord
  include Preferred::Preferable

  preference :nickname, :string
  preference :min_value, :decimal, default: 32.0
  preference :year, :integer, default: 2018
  preference :has_example, :boolean, default: true
  preference :birthday, :date, default: Date.today
end

example_model = ExampleModel.new
example_model.has_preference?(:min_value) # returns true
example_model.preferred_min_value # returns 32.0
example_model.preferred_min_value = 0 # sets min_value to 0
example_model.preference_default(:min_value) # returns 32.0
example_model.preference_type(:min_value) # returns :decimal

Complex example using Single Table Inheritance

Create base model

bin/rails g model strategy description:string type:string preference_hash:jsonb

Include Preferable in Strategy model

class Strategy < ApplicationRecord
  include Preferred::Preferable

  validates_presence_of :description

end

Define a models that extends Strategy

WithinRange Strategy

class WithinRange < Strategy
  # The minimum temperature value for the range
  preference :min, :decimal, default: 28.0
  # The maximum temperature value for the range
  preference :max, :decimal, default: 42.0

  def good?(value)
    (value => preferred_min) and (value <= preferred_max)
  end
end

BelowMaximum Strategy

class BelowMaximum < Strategy
  # The maximum temperature allowed
  preference :max, :decimal, default: 160.0

  def good?(value)
    value < preferred_max
  end
end

preferred

Development

Runtime

preferred

Usage

Simple Example

Complex example using Single Table Inheritance

Include Preferable in Strategy model

WithinRange Strategy

BelowMaximum Strategy