# Drop\_receiving\_element question **URL:** \ **Category:** Rails\ **Created:** [December 9, 2005, 8:56pm UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902 "2005-12-09T20:56:13Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![jeff.gray](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jeff.gray](https://www.ruby-forum.com/u/jeff.gray)\ **Post date:** [December 9, 2005, 8:56pm UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902/1 "2005-12-09T20:56:13Z")
Hi… First I’d like to say that this mailing list is EXTREMELY helpful to me. Thank all of you for answering questions. I am hoping that someone can help me with this problem: I have a draggable element being dropped on another element with this code: \<%= drop\_receiving\_element “element1”, ``` :accept => "item", :hoverclass => "item-active", :url => {:controller=> 'testcontroller', :action => 'test'} %> ``` I need to find out how to get the ID for this droppedOn element (in this case, “element1” - but how to pass it to controller?) And also the ID for the draggable element. How do I pass these to the controller? Is it possible to put javascript inside the :url parameter? Everytimg I try something like: :url=\>{:action=\>‘test’, :element1=\>“document.getElementById(‘this.parentNode’).id”} It will fail with this. Any ideas on how to pass these element IDs? Thanks in advance. ---
**Author:** ![jeff.gray](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jeff.gray](https://www.ruby-forum.com/u/jeff.gray)\ **Post date:** [December 9, 2005, 11:55pm UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902/2 "2005-12-09T23:55:46Z")
Gray, Jeffrey \ writes: > I need to find > out how to get the ID for this droppedOn element (in this case, â??element1â? > â?? but how to pass it to controller?) The DOM ID for the drop receiving element isn’t automatically passed back to the controller. However, there’s nothing stopping you from passing your own parameters back to the controller as part of the URL, for example: :url =\> { :controller =\> ‘testcontroller’, :action =\> ‘test’, :where =\> ‘element1’ } When the “test” action runs, it can check params[:where] to see which drop receiving element is calling it. > And also the ID > for the draggable element. That one’s easy: the DOM ID of the draggable element that’s dropped on your drop receiving element will automatically be included as the :id parameter in the method call–your controller just reads params[:id] to see what it is. > Is it possible > to put javascript inside the :url parameter? No–at least, not without a lot of work; the approaches above should make it unnecessary, anyway. You might, however, want some Javascript to be executed, however, when a droppable is dropped on your drop receiving element. For that you use one of the optional “callback” parameters to the drop\_receiving\_element helper, for example, in the :after, :loading, :complete, or other parameters. –Forrest ---
**Author:** ![jeff.gray](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jeff.gray](https://www.ruby-forum.com/u/jeff.gray)\ **Post date:** [December 10, 2005, 1:50am UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902/3 "2005-12-10T01:50:07Z")
Thanks for the help forrest. You stated I could do “where =\> ‘element1’” but how does Rails know it is a DOM object? ---
**Author:** ![jeff.gray](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jeff.gray](https://www.ruby-forum.com/u/jeff.gray)\ **Post date:** [December 10, 2005, 2:02am UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902/4 "2005-12-10T02:02:32Z")
Gray, Jeffrey \ writes: > Thanks for the help forrest. You stated I could do “where =\> ‘element1’” > but how does Rails know it is a DOM object? It doesn’t know–when you feed “:where =\> ‘element1’” to the url helper, all it knows is that you want to send an additional parameter called “where”, with value “element1” as part of the URL, so you’d get a URL that looks something like: [http://whatever.com/testcontroller/test?where=element1](http://whatever.com/testcontroller/test?where=element1) It doesn’t know “element1” is a DOM ID–it could be anything. The trick to this is that _you_ know the DOM ID, and when you write the Rails code to create the drop receiving element, _you_ can specify that ID as the value for the “where” parameter. If your web page has 3 different drop receiving elements, you write a drop\_receiving\_element helper for each one, and give each one a different “where” value, so that when the AJAX requests come in to it, it can tell the difference between them. This means that you don’t have to use DOM IDs at all–you could use any unique identifiers that your action can tell apart. –Forrest ---
**Author:** ![jeff.gray](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jeff.gray](https://www.ruby-forum.com/u/jeff.gray)\ **Post date:** [December 10, 2005, 3:34pm UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902/5 "2005-12-10T15:34:15Z")
Thanks again Forrest. However, I do not now the element ID…it is being produced by a sql query. But I know the parent id and child id…so I need to use JS to get the node. is this possible? ---
**Author:** ![jeff.gray](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/j/dc4da7/32.png) [@jeff.gray](https://www.ruby-forum.com/u/jeff.gray)\ **Post date:** [December 10, 2005, 6:18pm UTC](https://www.ruby-forum.com/t/drop-receiving-element-question/49902/6 "2005-12-10T18:18:40Z")
Gray, Jeffrey \ writes: > Thanks again Forrest. However, I do not now the element ID…it is being > produced by a sql query. But I know > the parent id and child id…so I need to use JS to get the node. is this > possible? Well, it is generally possible, but can be tricky–too tricky to be really “Rails-like”. One tool that’s a big help with something like this is to try something in Rails, then pull the page in question up in your browser, and tell the browser to “View Source”–look at the HTML source for the page that Rails generated and see why the Javascript you inserted isn’t quite coming through correctly, adjust, and try again. After doing this the first time I can often see what I’m doing wrong (usually something like missing quotes in the right place) and get it working on the next try. One thing that can make all of this hard is that Rails isn’t expecting Javascript in certain places, so sometimes it will “helpfully” try to escape some of the strings containing your Javascript so that it WON’T be executed as Javascript, so you might have to go through some gyrations to get it to work. Sorry I don’t have time to try some of this out to give you a working example–I’m a little busy today! As I think about it, though, you might see if there isn’t a different way to approach the problem; it sounds odd that the controller/view creating your page doesn’t know the id of an element on the page that it itself is rendering–after all, even if it’s coming from an SQL query, that query is still being done in your controller, so the controller still has access to the information. From my experience, the only time you need to use funny Javascript like this is when you need to know the DOM ID of something in your user interface that the user is actively changing–for example, the ID of an item being dropped on something–NOT to get the ID of a static fixture on the page, like a drop receiving element. So, you might be able to do what you want using the method I describe above, but it isn’t feeling right to me. Good luck! –Forrest