_form.html.erb

<% if current_user == @user %>
    <h2>Tilføj et indlæg:</h2>
    <%= simple_form_for([@user, @user.posts.build], :html => { :class => 'form-horizontal'}) do |f| %>
      <%= f.error_notification %>

      <div class="form-inputs">
        <%= f.input :title, :required => true, :autofocus => true %>
        <%= f.input :description, :required => true %>
        <%= f.input :location, :required => true %>
        <%= f.input :photo %>
      </div>

      <div class="form-actions">
        <%= f.button :submit, "Opret" %>
      </div>
    <% end %>
<% end %>

_modal.html.erb

<!-- Button trigger modal -->
<button class="btn btn-primary btn-lg" data-toggle="modal" data-target="#myModal">
  Opret nyt opslag
</button>

<!-- Modal -->
<div class="modal fade" id="myModal" tabindex="-1" role="dialog" aria-labelledby="myModalLabel" aria-hidden="true">
  <div class="modal-dialog">
    <div class="modal-content">
      <div class="modal-header">
        <button type="button" class="close" data-dismiss="modal" aria-hidden="true">&times;</button>
        <h4 class="modal-title" id="myModalLabel">Opret nyt indlæg</h4>
      </div>
      <div class="modal-body">
          <%= render 'form' %>
      </div>
      <div class="modal-footer">
        <button type="button" class="btn btn-default" data-dismiss="modal">Close</button>
      </div>
    </div><!-- /.modal-content -->
  </div><!-- /.modal-dialog -->
</div><!-- /.modal -->

_post.html.erb

<% @user.posts.sort_by(&:created_at).reverse.each do |p| %>
<div class="panel panel-default">
    <div class="panel-heading">
        <h2 class="panel-title"><%= link_to p.title, post_path(p.id) %></h2>
    </div>
    <div class="panel-body">
        <%= p.description %>
        <% if p.photo? %>
            <%= link_to p.photo.url do %>
                <%= image_tag p.photo.url(:medium) %>
            <% end %>
        <% end %>
    </div>
    <div class="panel-footer"><%= p.location %> | 
        Oprettet for <%= time_ago_in_words(p.created_at) %> siden | 
        af <%= link_to p.user.email, user_path(p.user_id) %> | 
        <% if current_user == @user %>
            <%= link_to 'Rediger', edit_user_post_path(p.user_id, p.id) %> |
            <%= link_to 'Slet', user_post_path(p.user_id, p.id), method: :delete %>
        <% end %>
    </div>
</div>
<% end %>

show.html.erb

<div class="page-header">
    <h2>Indlæg af <%= @user.first_name %></h2>
</div>

<% if current_user == @user %>
    <%= render 'modal' %>
<% end %>
<%= render 'post' %>