Exhibits and renderers

gistfile1.rb

class RailsTextPostRenderer
  def initialize(context)
    @context = context
  end

  def render(model)
    @context.render(partial: "/posts/text_body", locals: {post: model})
  end
end

class TextPostExhibit < SimpleDelegator
  def initialize(model, renderer)
    @model, @renderer = model, renderer
    super(model)
  end

  def render_body
    @renderer.render(@model)
  end
end

# Within the controller, and simplified without the ExhibitHelper
@post = TextPostExhibit.new(blog.post(params[:id]), RailsTextPostRenderer.new(self))

# When rendering JSON
@post = TextPostExhibit.new(blog.post(params[:id]), JSONTextPostRenderer.new(self))

#
#
# Which could then be refactored into...
#
#

class Exhibit < SimpleDelegator
  def initialize(model, renderer)
    @model, @renderer = model, renderer
    super(model)
  end

  def render_body
    @renderer.render(@model)
  end
end

# Now we have only one exhibit which acts as a decorator and we've decoupled the rendering mechanism
@post = Exhibit.new(blog.post(params[:id]), RailsTextPostRenderer.new(self))

# JSON uses the same exhibit but a different renderer
@post = Exhibit.new(blog.post(params[:id]), JSONTextPostRenderer.new(self))