Validation errors not showing up - Rails 4 - ruby-on-rails

Question

For some reason validation errors are not showing up.
my form
<%= form_for [#question.category, #question] do |f| %>
<% if #question.errors.any? %>
<div id="error_explanation">
<h2><%= pluralize(#question.errors.count, "error") %> prohibited this question from being saved:</h2>
<ul>
<% #question.errors.full_messages.each do |message| %>
<li><%= message %></li>
<% end %>
</ul>
</div>
<% end %>
<div class="field panel">
<%= f.label :question_type %><br>
<%= f.select :question_type, [ ["single","single"],["multiple","multiple"] ], selected: f.object.question_type %>
</div>
<div class="field panel">
<%= f.label :description %><br>
<%= f.text_field :description %>
</div>
<div class="field panel">
<%= f.label :image %><br>
<% if #question.image? %>
<div class="explanation-image text-center">
<%= image_tag #question.image_url(:resized) %>
<p>
<label>
<%= f.check_box :remove_image %>
Remove image
</label>
</p>
</div>
<% end %>
<%= f.file_field :image %>
<%= f.hidden_field :image_cache %>
</div>
<div class="field panel">
<%= f.label :explanation %><br>
<%= f.text_area :explanation, size: "30x10" %>
</div>
<div class="field panel">
<%= f.label :link_name %><br>
<%= f.text_field :link_name %>
</div>
<div class="field panel">
<%= f.label :link_url %><br>
<%= f.text_area :link %>
</div>
<div class="field panel">
<%= f.label :video_url %><br>
<%= f.text_area :video_url %>
</div>
<div class="field panel">
<%= f.label :category_id %><br><%= #category.title %>
<%= f.hidden_field :category_id %>
</div>
<div class="actions">
<br>
<%= f.submit 'Submit', class:"button round success" %> <%= link_to 'Back', category_questions_path, class: "button round alert" %>
</div>
<% end %>
this is the model
class Question < ActiveRecord::Base
belongs_to :category
has_many :choices
mount_uploader :image, ImageUploader
validates :description, length: {
minimum: 6
}
validates :link, presence: true
end
and parts of the controller
def edit
#category = Category.find(params[:category_id])
#question = #category.questions.find_by(id: params[:id])
end
def update
respond_to do |format|
if #question.update(question_params)
format.html { redirect_to category_question_url(#question.category, #question), notice: 'Question was successfully updated.' }
format.json { render :show, status: :ok, location: #question }
else
format.html {
#category = Category.find(params[:category_id])
#question = #category.questions.find_by(id: params[:id])
render action: :edit
}
format.json { render json: #question.errors, status: :unprocessable_entity }
end
end
end
the error messages code is directly from the scaffolding. i haven't touched it. if i try to edit a question and save it while lets say link field is empty it will reload the edit action correctly but no error message will pop up.
Any clues?

Answer 1

If it fails to save, you redefine the #question variable, before rendering out the page.
#question = #category.questions.find_by(id: params[:id])
this will delete the object which failed to save and was holding the validation errors, and replace it with the one loaded out of the database. Don't do this. I think if you just delete this line it might work ok.