Unobtrusive Scripting

Write a Dynamic Form With link_to

Deleting a post or a comment currently needs a form so that we can use the _method trick to trigger a DELETE action. Rails provides a way that we can do this simply with the link_to helper.

For example:

<%= link_to 'Delete', post_path(, method: :delete, data: { confirm: "Are you sure want to delete '#{post.title}'?"} %>

This will render into:

<a data-confirm="Are you sure want to delete 'post_title_here'?" rel="nofollow" data-method="delete" href="..." >Delete</a>

Rails monitors the data-method and data-confirm data attributes for special processing with a Javascript library that it ships with, the jquery-rails library. This behavior is called "unobtrusive scripting". It is named "unobtrusive scripting" because the Javascript code that facilitates this is not intertwined with the markup.

In this case, it'll trigger a HTTP DELETE after the user confirms a dialog box on the UI.

For more about Unobtrusive Scripting behaviors, see:

Javascript Include Tag and CSRF meta tags

If we want our link_to to work as a dynamic form, we need to enable Javascript on our page. To do that we'll need a <script> tag for our application's main Javascript page. Rails gives us a useful helper for creating this script tag when we need it.

  <title>Blog App</title>
  <%= javascript_include_tag 'application' %>
  <%= csrf_meta_tags %>

Notice that we also have csrf_meta_tags . This dynamically creates a csrf token for our dynamic form to use. Our link_to dynamic form is using Javascript, and when using Javascript to send a form, we will need to include this csrf meta token. Rails requires it by default.