Question

Let’s say I have a model called Article:

class Article < ActiveRecord::Base
end

And then I have a class that is intended to add behavior to an article object (a decorator):

class ArticleDecorator

  def format_title
  end

end

If I wanted to extend behavior of an article object, I could make ArticleDecorator a module and then call article.extend(ArticleDecorator), but I’d prefer something like this:

article = ArticleDecorator.decorate(Article.top_articles.first) # for single object

or

articles = ArticleDecorator.decorate(Article.all) # for collection of objects

How would I go about implementing this decorate method?

Answer 1

What exactly do you want from decorate method? Should it simply add some new methods to passed objects or it should automatically wrap methods of these objects with corresponding format methods? And why do you want ArticleDecorator to be a class and not just a module?

Updated:

Seems like solution from nathanvda is what you need, but I’d suggest a bit cleaner version:

module ArticleDecorator

  def format_title
    "#{title} [decorated]"  
  end

  def self.decorate(object_or_objects_to_decorate)
    object_or_objects_to_decorate.tap do |objects|
      Array(objects).each { |obj| obj.extend ArticleDecorator }
    end
  end

end

It does the same thing, but:

1. Avoids checking type of the arguments relying on Kernel#Array method.
2. Calls Object#extend directly (it’s a public method so there’s no need in invoking it through send).
3. Object#extend includes only instance methods so we can put them right in ArticleDecorator without wrapping them with another module.