In recent versions of Rails it is quite a bit easier to render partials and pass locals to them. Instead of this.
<%= render :partial => 'form', :locals => { :item => @item } %>
You can do this.
<%= render 'form', :item => @item %>
I don’t do this in the Nifty Scaffold generator to keep backwards compatibility, but I’ll change this in a future release.
As for whether it’s acceptable to use instance variables in partials. I think it is. In all practicality, what is the downside? Certainly things can get out of hand if you aren’t consistent, but I like to apply these guidelines.
-
Never create an instance variable just to share it between partials. Usually this means you will only be sharing the controller resource object.
-
If the partial is the same name as the resource, pass it as a local with
<%= render @item %>. -
If the partial will be shared across multiple controllers then only use locals.
This is what works well for me anyway.
Bonus tip: if you find yourself passing in a lot of locals into a partial and you want some of them to be optional, create a helper method which renders the partial. Then always go through the helper method so you can make a clean interface with optional args for rendering the partial.