acts_as_interface

INSTALL

gem install acts_as_interface

DESCRIPTION

In the spirit of self documenting code, acts_as_interface allows you to easily define abstract_methods and callbacks just by listing them at the top of a superclass or module. Child classes or classes that include the module must implement abstract_methods or a NotImplementedError is raised when the method is called.

EXAMPLE

class Person
  include ActsAsInterface

  # all subclasses are expected to define id and worth
  abstract_methods :id 
  abstract_methods :worth, :visibility => :private

  # defines an empty method called before_sleep, which I call in sleep.  Subclasses can override before_sleep if they need to.
  callbacks :before_sleep 

  def sleep
    before_sleep
    close_eyes
    dream
  end
end

class Student < Person
  def id
    student_id
  end

  def before_sleep
    set_alarm
  end

  private  
  def worth
    0
  end
end

class Employee < Person
  def id
    employee_number
  end

  private
  def worth
    salary
  end
end

OPTIONS

Both abstract_methods and callbacks take options that accept the following keys

visibility - :private, :protected, or :public (default is public)

abstract_methods :internal_counter, :visibility => private

for - :class or :instance (default is instance) - is the method a class method or an instance method?

abstract_methods :category, :for => :class

USING WITH DIFFERENT TYPES OF INHERITANCE

SUBCLASSING

class Person
  include ActsAsInterface
  abstract_methods :dance, :eat
end

class Student < Person
  # define dance and eat here
end

MODULE (on include)

module ActsAsPerson    
  def self.included(base)
    base.instance_eval do
      include ::ActsAsInterface
      abstract_methods :name, :dance
    end
  end
end

class Student < ActiveRecord::Base
  include acts_as_person
  
  # define name and dance here
  # still works if name or dance is previously defined (ie if name were an attribute of the Student model - t.string :name)
end

MODULE (from method call)

module ActsAsPerson    
  module ClassMethods
    def acts_as_person
      include ::ActsAsInterface
      abstract_methods :name, :dance
    end
  end
  
  def self.included(base)
    base.extend(ClassMethods)
  end
end

class Student < ActiveRecord::Base
  include acts_as_person
  acts_as_person # apply interface
end

Credits

ActsAsInterface is currently maintained by Philippe Huibonhoa and funded by BookRenter.com.

CONTRIBUTING

Check out the latest master to make sure the feature hasn't been implemented or the bug hasn't been fixed yet
Check out the issue tracker to make sure someone already hasn't requested it and/or contributed it
Fork the project
Start a feature/bugfix branch
Commit and push until you are happy with your contribution
Make sure to add tests for it. This is important so I don't break it in a future version unintentionally.
Please try not to mess with the Rakefile, version, or history. If you want to have your own version, or is otherwise necessary, that is fine, but please isolate to its own commit so I can cherry-pick around it.