Custom validate doesn't appear to be adding errors

Question

I am trying to stop a user voting for themselves using validation.

Submitting a self vote renders the basic flash "Vote not accepted." but doesn't add the validation error "You cannot vote for your self".

How can I add the error to the flash?

In my model I have

class Imagevote < ActiveRecord::Base
    validate :cannot_vote_for_self


    def cannot_vote_for_self
        if voter_id == voted_id
        errors.add(:base, "You cannot vote for your self")
        end
    end
end

In my controller I have

class ImagevotesController < ApplicationController

    def create
        @imagevote = Imagevote.new(imagevote_params)
        @collection = Collection.find(params[:imagevote][:collection_id])
        @imagevote.voted_id = @collection.user_id
        if @imagevote.save
            flash[:success] = "Vote accepted."
            redirect_to @imagevote
        else
            flash[:success] = "Vote not accepted."
            redirect_to :back
        end
    end

    def update
        @imagevote = Imagevote.find(params[:id])
        @collection = Collection.find(params[:imagevote][:collection_id])
        @imagevote.voted_id = @collection.user_id
        if @imagevote.update_attributes(imagevote_params)
            flash[:success] = "Vote changed."
            redirect_to @imagevote
        else
        flash[:success] = "Vote not accepted."
            redirect_to :back
        end
    end

I think the errors are inserted here in my application layout view

<% flash.each do |key, value| %>
        <%= content_tag(:div, raw(value), class: "alert alert-#{key}") %>
<% end %> 

Answer 1

Following

errors.add(:base, "You cannot vote for your self")

would add errors to an instance of Model Imagevote. They will not be added to flash hash.

In order to display the validation error messages, you need following code in

<% if @imagevote.errors.any? %>
    <div id="error_explanation">
      <h2><%= pluralize(@imagevote.errors.count, "error") %>
        prohibited this user from being saved:</h2>
      <ul>
        <% @imagevote.errors.full_messages.each do |msg| %>
          <li><%= msg %></li>
        <% end %>
      </ul>
    </div>
  <% end %> 

in the view where you are creating/updating an Imagevote object.

EDIT

Update the cannot_vote_for_self validation method as below:

   def cannot_vote_for_self
        if voter_id == voted_id
        errors.add(:vote, "You cannot vote for your self")
        end
    end

Set the flash message in controller action as below:

  def create
        @imagevote = Imagevote.new(imagevote_params)
        @collection = Collection.find(params[:imagevote][:collection_id])
        @imagevote.voted_id = @collection.user_id
        if @imagevote.save
            flash[:success] = "Vote accepted."
            redirect_to @imagevote
        else
            flash[:alert] = "Vote not accepted."
            flash[:alert] << @imagevote.errors[:vote].first unless @imagevote.errors[:vote].nil?
            redirect_to :back
        end
    end