#View
###Form
#####Adding class to form and to elements
<%= form_for @article, html: {class: "form"} do |f| %>
<div class="form-group">
<%= f.label :title %><br>
<%= f.text_field( :text, {:class => "form-control"}) %>
</div>
<%= f.submit({:class => "btn"}) %>
<% end %>###Links
#####Adding class to links
<%= link_to 'Show', article_path(article), class: "btn btn-default" %>