Question

I have a fairly complex view that has multiple forms, lots of validations on those forms, paginations, and other features. When validations fail, I like to use render because then you can be more specific about what errors occurred in the forms. However, when I use render different compiler errors crop up such as “undefined method `total_pages’ for []:Array” and “undefined model_name”. Is this a situation when I have to use redirect_to or is it feasible to somehow work around the errors that are coming up when the view is being rendered. Thanks a bunch!

Answer 1

You should grasp things in their perspective.

Why is render used instead of redirect:

• when you use render, you pass the instantiated object

• this object, newly created or updated, received some params

• when attempting to save the object, validation was triggered and, if unsuccessful, added errors to the current instance

• so your object in memory contains validation errors.

But when you use redirect, you restart with a fresh stack which doesn’t know anything about the former object in memory, there could not be any magic:

• either the object is saved and you can get the persisted data from database

• or if it’s not saved, you can have some information you previously stored in session

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To answer your question a bit closer: before you use render, you have to instantiate all objects needed by the page.

It’s just logic the view fails if the expected instance variables are missing.