Methods in Rails modules

Modules are commonly used to to group constants holding possible attribute values. Like in the example below we have a Order class and it has attribute status.

Status can hold different values as pending, confirmed, cancelled etc.

class Order < ApplicationRecord

  module Status
    PENDING = 'Pending'
    CONFIRMED = 'Confirmed'
    CANCELLED = 'Cancelled'
    DECLINED = 'Declined'
    COMPLETED = 'Completed'
  end

  validates_inclusion_of :status, in: [Status::PENDING, Status::CONFIRMED, Status::CANCELLED, Status::DECLINED, Status::COMPLETED]
end

When a new order is placed or existing order updated we want to ensure that status attribute contains valid value. We are using rails validation method validates_inclusion_of to achieve that. Since we are using all status values if we introduce a new status then we also need to change validation.

It can be avoided. Create a class all method inside module Status.

class Order < ApplicationRecord

  module Status
    PENDING = 'Pending'
    CONFIRMED = 'Confirmed'
    CANCELLED = 'Cancelled'
    DECLINED = 'Declined'
    COMPLETED = 'Completed'

    def self.all
      constants.map {|const| const_get(const)}
    end
  end

  validates_inclusion_of :status, in: Status.all
end

You can add more methods which can be used in other places. Like in example below I have a method active? in order class. Order is considered as active when its pending or confirmed.

def active?
  status.in?([Status::PENDING, Status::CONFIRMED])
end

Here as well we can add another class method active in status module and use it in active? method like below:

class Order < ApplicationRecord

  module Status
    PENDING = 'Pending'
    CONFIRMED = 'Confirmed'
    CANCELLED = 'Cancelled'
    DECLINED = 'Declined'
    COMPLETED = 'Completed'

    def self.all
      constants.map {|const| const_get(const)}
    end

    def self.active
      [Status::PENDING, Status::CONFIRMED]
    end
  end

  validates_inclusion_of :status, in: Status.all

  def active?
    status.in?(Status.active)
  end
end

Hope this helps you in writing minimal code and avoids mistakes as well.

Happy coding!!!