HOWTOs for Ruby on Rails and JavaScript

Copy a Paperclip attachment to another record

Just assign the existing attachment to another record:

new_photo = Photo.new
new_photo.image = old_photo.image

Paperclip will duplicate the file when saving.

To use this in forms, pimp your attachment container like this:

class Photo < ActiveRecord::Base
  has_attached_file :image
  
  attr_accessor :copy_of

  def image_url
    if copy_of
      copy_of.url
    else
      image.url
    end
  end
end

And in the controller do:

new_photo = Photo.new(:copy_of => old_photo)

Edit

Force absolute URLs in views throughout a response

This is more tricky than it should be because url_for, asset_path, etc. all rely on different mechanisms.

Anyway, you can use the attached trait like this:

class ExampleController < ApplicationController
  does 'host_enforcement', :for => 'some_action'
end

Short explanation:

asset_host is used for links to stylesheets and javascripts
asset_host belongs to ActionController::Base -- changes are persistent and will not be reset after a request
rewrite_options is used by the ..._path methods in the views
^...

Edit

Unobtrusive JavaScript and AJAX

Attached (see below) is some code to allow using unobtrusive JavaScript on pages fetched with an AJAX call.

After you included it, you now do not use the usual

$(function() { 
  $('.some_tag').activateStuff(); 
});

any more, but instead you write

$.unobtrusive(function() {
  $(this).find('.some_tag').activateStuff();
});

that is

$.unobtrusive() instead of $()
don't do stuff to the whole page, but just to elements nested below $(this)

Normal pages work as before (your $.unobtrusive functions are ca...

Edit