Form using HAML alongside Batman.js

_form.html.haml

%fieldset
  %legend
    %span{"data-hideif" => "post.id"} New Post
    %span{"data-showif" => "post.id"} Edit Post
  #error-explanation.alert-message.block-message.error{"data-showif" => "post.errors.length"}
    %p
      %strong
        %span{"data-bind" => "post.errors.length"}
        %span{"data-bind" => "'error' | pluralize post.errors.length"}
        prevented this post from being created:
    %ul
      %li{"data-bind" => "error.message", "data-foreach-error" => "post.errors"}
  .clearfix{"data-addclass-error" => 'post.errors.title.length'}
    %label{:for => "post_title"} Title
    .input
      %input#post_title.span8{"data-bind" => "post.title", :name => "post[title]", :size => "30", :type => "text"}
%fieldset
  .clearfix{"data-addclass-error" => 'post.errors.content.length'}
    %label{:for => "post_content"} Description
    .input
      %textarea#post_content.span8{:cols => "40", "data-bind" => "post.content", :name => "post[content]", :rows => "20"}
.actions
  %input.btn.btn-primary{:name => "commit", :type => "submit", :value => "Submit"}
    %a.btn{'data-route' => 'Post'} Cancel