Using Partial view

View filename that starts with underscore are called partial:

_form.html.erb
_nav.html.erb

When using render function, we specify the partial name without the underscore:

<%= render 'nav' %>

If the partial file is not in the same folder, say views/layouts/_nav.html.erb, we can include the path.

<%= render 'layouts/nav' %>

Sometimes we need to pass variable into partial. We can do that by specifing them in hash.

<%= render 'layouts/nav', key: 'value' %>