Module: MoodSwing

Defined in:
lib/mood_swing.rb,
lib/mood_swing/version.rb

Overview

Allows polymorphic behavior based on the value of an attribute by including a module dynamically.

Constant Summary collapse

VERSION = 
"0.0.1"

Instance Method Summary collapse

Instance Method Details

#mood_trigger(reader, options = {}) ⇒ Object

reader is the value to use as the basis of the included module. The convention for naming the include is: YourClass::YourNameExtension

An example would be:

class Dog < ActiveRecord::Base

mood_trigger 'breed'

def bark
  puts 'woof'
end

end

module Dog::HoundExtension

def bark
  puts 'Hoooooowl'
end

end

When a instance of dog is initialized the breed attribute is read and it’s value is used to extend the current instance’s behavior with the module matching following the previously mentioned convention. If the Dog instance’s breed was “Hound” then it would be extended with the Dog::HoundExtension. Now when you call @dog.bark, your dog will howl instead of woof.

The module is updated when the attribute changes. An example of the behavior to expect with a new object is:

spot = Dog.new spot.bark

> “woof”

spot.breed = “hound” spot.bark

> ‘Hoooooowl’

If your attribute writer is different from the reader, then you can pass in :writer => “your_writer_method” and it will use that. This is the case when using a polymorphic belongs_to accessor as the attribute.

belongs_to ‘body’, :polymorphic => true mood_trigger ‘body_type’, :writer => ‘body’



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# File 'lib/mood_swing.rb', line 42

def mood_trigger(reader, options ={})
  options[:writer] ||= reader

  define_method("#{options[:writer]}_with_extension=") do |value|
    self.send "#{options[:writer]}_without_extension=", value
    self.send "#{reader}_extension!"
    self.send reader
  end

  define_method("#{reader}_extension!") do
    begin
      self.extend "#{self.class}::#{self[reader].classify}Extension".constantize
    rescue NameError
    end
  end

  class_eval do
    alias_method_chain "#{options[:writer]}=", 'extension'
    after_initialize "#{reader}_extension!"
  end
end