Change
<%= @event.attributes.each do |attr_name, attr_value| %>
To
<% @event.attributes.each do |attr_name, attr_value| %> ## Removed =
You are seeing a hash displayed in the view because you are rendering @event.attributes
which I suppose you don't need to.
<% %>
is for evaluation of Ruby expression and <%= %>
for evaluation plus rendering the result of Ruby expression. In your case, you simply need <% %>