Module: Conversions::ActiveRecordAccessors

Defined in:
lib/conversions/active_record_accessors.rb

Overview

Implements new accessor classmethods to define conversion accessors on active record classes.

Instance Method Summary collapse

Instance Method Details

#conversion_accessor(attribute, options = {}) ⇒ Object

Adds conversion methods to the model for a certain attribute.

Options:

  • :internal: The unit of the internal value

  • :external: The unit of desired external value

  • :scale: If a scale is given, the external value is automatically rounded on the specified scale.

Examples:

require 'conversions'

class Flight
  extend Conversions::ActiveRecordAccessors

  attr_accessor :distance
  conversion_accessor :distance, :internal => :kilometers, :external => :miles, :scale => 2

  def initialize(distance)
    self.distance = distance
  end
end

flight = Flight.new(1200)
flight.distance_in_miles #=> 745.65, rounded down to two decimals as specified in :scale

When used as a plugin for Rails, the ActiveRecord::Base is automatically extended.

class Car < ActiveRecord::Base
  conversion_accessor :length, :internal => :kilometers, :external => :miles
end



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# File 'lib/conversions/active_record_accessors.rb', line 36

def conversion_accessor(attribute, options={})
  if options[:internal].nil? or options[:external].nil?
    raise ArgumentError, "Please specify both :external and :internal metrics."
  end
  define_method "#{attribute}_in_#{options[:external]}" do
    v = send(attribute)
    v ? v.send(options[:internal]).to(options[:external], options[:scale]) : nil
  end
  define_method "#{attribute}_in_#{options[:external]}=" do |v|
    send("#{attribute}=", v.to_f.send(options[:external]).to(options[:internal]))
  end
end