I can easily use if else conditions in a view.
<% if condition_one %>
<% else %>
<div class="form_for_new_object" >
1: Not supposed to put too much logic in views?
With some guidelines, "too much" is up to you IMO. Seems like the mood of the gurus these days is for short routines so that you can have one master routine call a bunch of short routines. That way you have one place to read a succinct description of the steps of the logic flow, and you can go look at details one at a time. I find this to be an effective pattern.
While that is often discussed for logic, I believe it applies to views as well. I like my actual view file to be the description of the logic flow of the view (if there is one) -- which means when it is complex enough, it includes a bunch of partials. Not so much for the reusability, just the ability to break the process or the overall makeup of the view down into a simple story.
Sometimes a bunch of files feel annoying for sure when you're doing your first pass at the work, but when the app has been running for 6 months then you go back to it, a couple hundred lines of view code intertwined with a bunch of logic which actually controls what shows up and what does not -- its going to take you a while to deduce what's going on.
What I do is start by putting everything in one file, one action. I don't really know where it will make sense to break it up until I see it closer to being finished. Plus as you say, it's easier to work with all in one place. So, I start with one file, and then when done, I break it into pieces. You have to be aware that right now as you're writing the code, you have all your vars, logic, and decision justifications in your head. You can see through all noise of the code. In 3 months you won't have that. It's at that time that you'll appreciate the breakdown of it into pieces.
2: My the action that calls the page creates instance variables for
both the desired and undesired display items and has been getting a bit
tricky assuring that I don't do a find on a nil object ...
Is it perfectly fine to use if/else clauses and complicated actions to
create display pages or should I bite the bullet and create lots of
clean html views and lots of separate actions, one for each contingency?
IMO, nothing wrong with conditional logic inside one action to determine what needs to be displayed. but follow that pattern above. Use the action method to outline the steps of what has to happen, and put the details of the work into seperate (protected or priviate) methods.
I build a lot of non-Ajax admin-type pages where editing a model involves a series of on-screen forms. I use one action which handles everything. The action method has a decision tree based on which button was clicked in the UI -- that dictates what logic has to be performed and which view pieces will be assembled.
For a simplistic illustration, let's assume we have a series of three forms: Signup, Details, Summary. Each form has a Save button, a cancel button, and nav buttons to allow me to jump to any of the three forms. Off the top of my head, so...