This blog is part of our Rails 5 series.

Before Rails 5, partials name should start with underscore and should be followed by any combination of letters, numbers and underscores.

This rule was required because before commit, rendering a partial without giving :object or :collection used to generate a local variable with the partial name by default and a variable name in ruby can’t have dash and other things like that.

In the following case we have a file named _order-details.html.erb. Now let’s try to use this partial.

<!DOCTYPE html>
  <%= render :partial => 'order-details' %>

We will get following error, if we try to render above view in Rails 4.x.

ActionView::Template::Error (The partial name (order-details) is not a valid Ruby identifier;
make sure your partial name starts with underscore,
and is followed by any combination of letters, numbers and underscores.):
    2: <html>
    3: <body>
    4: Following code is rendered through partial named _order-details.erb
    5: <%= render :partial => 'order-details' %>
    6: </body>
    7: </html>

In the above the code failed because the partial name has a dash which is not a valid ruby variable name.

In Rails 5, we can give our partials any name which starts with underscore.