Rails: DEPRECATION WARNING: @var will no longer be implicitly assigned to local_var.

I just ran into an interesting warning and since it took me a few minutes to figure it out I thought I share it here.

I’m rendering a partial template like this:

render :partial => 'list_items/list_item', :locals => { :list => @list, :list_items => @list_item}

Now, when running this code I got this deprecation warning:

DEPRECATION WARNING: @list_item will no longer be implicitly assigned to list_item. 
(called from _run_erb_app47views47list_items47_list_item46html46erb_locals_list_list_item_list_items_object 
at /home/stefan/projects/Memento/app/views/list_items/_list_item.html.erb:1)

The problem here was that in the partial I’m using the local variables are named list and list_item, in the render call however I’m passing in list and list_items. Everything still works because rails implicitly assigns @list_item to the local variable list_item. This is what the warning says…

So the fix is simply removing the additional “s”.

render :partial => 'list_items/list_item', :locals => { :list => @list, :list_item => @list_item}

Not specifically hard but yet another prove that taking “a close look” at your own code is always difficult ;-) I bet a peer what have see the problem in a sec …