ActionView::Helpers::DebugHelper
Methods
D
Included Modules
Instance Public methods
debug(object)

Returns a YAML representation of object wrapped with <pre> and </pre>. If the object cannot be converted to YAML using to_yaml, inspect will be called instead. Useful for inspecting an object at the time of rendering.

@user = User.new({ username: 'testing', password: 'xyz', age: 42})
debug(@user)
# =>
<pre class='debug_dump'>--- !ruby/object:User
attributes:
  updated_at:
  username: testing
  age: 42
  password: xyz
  created_at:
</pre>

Source: show | on GitHub 

# File actionview/lib/action_view/helpers/debug_helper.rb, line 24
def debug(object)
  Marshal::dump(object)
  object = ERB::Util.html_escape(object.to_yaml)
  content_tag(:pre, object, class: "debug_dump")
rescue # errors from Marshal or YAML
  # Object couldn't be dumped, perhaps because of singleton methods -- this is the fallback
  content_tag(:code, object.inspect, class: "debug_dump")
end