Highlight link based on current page in rails

This is common pattern in website navigation, where it highlights the link (usually by setting class=”active”) that took you to the current page while you are on that page.

First, define a helper:

def is_active?(page_name)
  "active" if params[:action] == page_name
end

Then call it in your link_to’s in your layout as such:

link_to 'Home', '/', :class => is_active?("index")
link_to 'About', '/about', :class => is_active?("about")
link_to 'contact', '/contact', :class => is_active?("contact")

This effect is achieved due to how link_to handles being passed nil for its :class, so when is_active? returns nil (because its not the current page), link_to outputs nothing as its class (not class=”” as you might expect).