_form.html.erb

<%= form_for :post, :url => { :action => :create } do |f| %>
  <% if @post.errors.any? %>
    <div id="errorExplanation">
      <h2><%= pluralize(@post.errors.count, "error") %> prohibited this post from being saved:</h2>
      <ul>
        <% @post.errors.full_messages.each do |msg| %>
          <li><%= msg %></li>
        <% end %>
      </ul>
    </div>
  <% end %>
  <p>
    <%= f.label :title %><br>
    <%= f.text_field :title %>
  </p>

  <p>
    <%= f.label :text %><br>
    <%= f.text_area :text %>
  </p>

  <p>
    <%= f.submit %>
  </p>
<% end %>