Poppy

Introduction

Simple Polymorphic Enumerations

Installation

Add this line to your application's Gemfile:

gem 'poppy'

And then execute:

$ bundle

Or install it yourself as:

$ gem install poppy

Usage

Basic

class Bread < Poppy::Enum
  values :white, :multigrain, :gluten_free
end

Using an enum value

> bread = Bread::WHITE
> bread 
=> Bread::WHITE

> bread.humanize
=> White

Listing all enum values

> Bread.list
=> [Bread::WHITE, BREAD::MULTIGRAIN, Bread::GLUTEN_FREE]

> Bread.collection
=> [['White', 'white'], ['Multigrain', 'multigrain'], ['Gluten free', 'gluten_free']

Custom values

Each enumeration value is able to define its own behavior. This makes our enumerations much more polymorphic. By defining classes we can decide the behavior each enumeration value has. Each value added to the enumeration will be created by instantiating the matching class

E.g. Bread::WHITE is created from the value :white. It is instantiated by the class Bread::White.

If no matching class exists a class will be created before it is instantiated

Never instantiate a class directly. Enum::Value.new != Enum::VALUE

class Bread < Poppy::Enum
  values :white, :multigrain

  private

  class White
    include Poppy::Value

    def enjoyed_by_kids?
      true
    end
  end

  class Multigrain
    include Poppy::Value

    def enjoyed_by_kids?
      false
    end
  end
end

white = Bread::WHITE
multi = Bread::MULTIGRAIN

puts white.enjoyed_by_kids? # true
puts multi.enoyed_by_kids? # false

Each enumeration value is just a Poro. Each value has an interface of one method, #humanize. More methods can be added to build a more robust interface. If not using Poppy::Rails humanize can be omitted.

Poppy::Value by default, defines humanize to be the demodulized class name humanized and capitalized. You are free to implement this however you would like.

E.g.

class Bread < Poppy::Enum
  values :white, :multigrain

  class White
    def humanize
      'Black'
    end
  end

  class Multigrain
    extend Poppy::Value
  end
end

Polymorphism

By giving each Enumeration value behavior we can remove switch statements from our codebase.

bread = Bread::WHITE

case bread
when Bread::WHITE
  puts 'My kid will love this'
when Bread::MULTIGRAIN
  puts 'My kid will play bread frisbee'
when Bread::GLUTEN_FREE
  puts 'My kid will play bread frisbee'
end

becomes

if bread.enjoyed_by_kids?
  puts 'My kid will love this'
else
  puts 'My kid will play bread frisbee'
end

ActiveRecord Integration

See the Poppy Rails Gem for a simple integration with ActiveRecord for persistance. Enum arrays are also supported for postgreSQL databases.

API

Poppy::Enum

.value_for

> Bread.value_for(:white)
=> Bread::WHITE

.values

> Bread.list_keys
=> [:white, :multigrain, :gluten_free]

.list

> Bread.list
=> [Bread::WHITE, BREAD::MULTIGRAIN, Bread::GLUTEN_FREE]

.valid?

> Bread.valid?(Bread::WHITE)
=> true

.key_for

> Bread.key_for(Bread::WHITE)
=> :white

.collection

> Bread.collection
=> [['White', 'white'], ['Multigrain', 'multigrain'], ['Gluten free', 'gluten_free']

• element.first is defined by the humanized value

For use with the Rails form builder

Poppy::Value

#humanize

> Bread::WHITE.humanize
=> White