REST path for "new from copy"

For certain models, I wish to provide functionality that allows a user to create a new record with 开发者_开发百科default attributes based on copy of an existing record.

I'm wondering what would be the correct restful route for this.

My initial thinking is that it could be a parameter to the new action. I.e. to borrow from the the Rails Guides examples, instead of just:

GET : /photos/new

Also allow:

GET : /photos/new/:id

...where :id is the id of the record to use as a template. The response would be a new/edit form, same as with a plain old new but the values would be pre-filled with data from the existing record. The parameter (or absense of it) could be easily handled by the new controller method.

The alternative seems to be to create a new controller method, for example copy which would also accept an id of an existing record and response with the new form as above. This seems a little 'incorrect' to me, as the record is not actually being copied until the user saves the new record (after probably editig it somewhat).

TIA...

UPDATE: my question is not "how do I do this in rails?", it's "is it RESTful?"

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my question is not "how do I do this in rails?", it's "is it RESTful?"

No, it isn't. For that matter, neither is GET /photos/new. Rails seems to be hopelessly mired in the past, where it was considered haute programme for a GET on a URI to return an HTML form which would then POST x-www-form-urlencoded data back to that same URI. The opacity of that POST forces them to invent new verbs-as-URI's like /photos/new, when you could be using PUT instead, or at least POST with the same media type.

The simplest way to make a copy of an HTTP resource RESTfully is:

GET /photos/{id}/ -> [representation of a photo resource]
...make modifications to that representation as desired...
POST /photos/ <- [modified representation]

If you're implementing this for browsers, you should be able to perform those actions via Ajax quite easily, using an HTML page sitting perhaps at /photos/manager.html/ to drive the interaction with the user.

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You can try to use nested resources. I'm not exactly sure about structure of you application, but in general using nested photos will look somehow like this:

routes.rb

resources :photos do
  resources :photos
end

photos_controller.rb

before_filter :find_parent_photo, :only => [:new, :create]

def create
  @photo = Photo.new params[:photo]
  if @parent_photo.present?
    # fill some @photo fields from @parent_photo
  end
  @photo.save

  respond_with @photo
end

def find_parent_photo
  @parent_photo = Photo.find(params[:photo_id]) if params[:photo_id].present?
end

new.html.haml

= form_for [@parent_photo, @photo] do |f|
  -# your form code

previously when you wanted to add a link to photo creation you wrote something like that

= link_to "new photo", [:new, :photo]

now if you want to add a link to photo creation based on foto @photo1

= link_to "new photo based on other one", [:new, @photo1, :photo]

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You should be able to match a route like so:

match 'photos/new/:photo_id' => 'photos#new

or you could just pass a :photo_id parameter in the url and handle it in the controller:

'/photos/new?photo_id=17'

Example using helper method: new_photo_path(:photo_id => 17)

Edit: I don't know if this conforms to REST

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It may be over the top, but you could do something like this:

class PhotoCopiesController < ApplicationController
  def new
    @photo = Photo.find(params[:photo_id]).dup
  end

  def create
  end
end

and

resources :photo_copies, :only => [:new, :create]

and

= link_to 'Copy', photo_copy_path(:photo_id => @photo.id)