Render or redirect based on validation of instance in create/update
Prefill in form values based on an instance
Print out full error messages based on an invalid instance
Introspect on errors for a field
Apply an error class to a field conditionally based on errors on a field
Requirements
Validations
Add validations to Author such that...
name is not blank
email is unique
phone_number is exactly 10 digits long
Add validations to Post such that...
title is not blank
content is at least 100 characters long
category is either "Fiction" or "Non-Fiction"
Basic Routes & Controllers
Create controllers for both models.
Create show, new, edit, create, and update routes for both models.
Define controller actions for show, new, and edit.
Define the "valid path" for the create and update controller actions.
Define the "invalid path" for the create and update controller actions.
Forms
Create forms with form_tag for both models' new and edit actions.
Prefill already-submitted forms with the invalid data when re-rendering.
Display a list of errors at the top of forms when an invalid action is
attempted. They should be contained in an element with id
error_explanation, and each error should have its own <li>.
Conditionally wrap each field in a .field_with_errors div if it has errors.