Rails: Should partials be aware of instance variables?

Question

Ryan Bates\' nifty_scaffolding, for example, does this

edit.html.erb

<%= render :partial => \'form\' %>

new.html.erb

Answer 1

I vote for a) for a very specific reason -- DRY! If you start passing a variable like that, the next thing you know it's a mess. Let's say you need to change the way your variable is named or something else about it. You'll need to go to ALL your views and change them instead of ONE partial.

Also, if you change your partial it will change on all your views, so you'll need to know which views are used. A proper IDE should be able to help you with that, but I also like having a small comment section at the top of the view where I just mention where it's used and why. This helps another programmer and it helps you to remember in case you need to come back to a partial and modify. But the whole point of the partial is to call it WITHOUT having to pass anything from the view, so that you don't have to modify all places where partial is called from if that variable changes somehow.

Ultimately this is a design choice, and to be honest unless you are running a facebook the extra lookup you do is not that big of a deal, but it's just not very DRY.

P.S.: Just thought about it. You can actually abstract the way you call partial in a helper method, so then if the way you call your partial needs to change, you just need to modify one place.