Accessing the link_to helper in a Rails controller and adding a link to a flash message

In my food planning app, after clicking a link to add all recipe ingredients to a shopping list, I display a flash message that looks like:

38 items added to your Grocery list.

Which is actually:

[calculated integer] [pluralized word] added to your [list name] list.

After having this feature in place for a while, I found myself wanting to be able to click on the list name in the flash message to take me to that shopping list. So how do you put a link in a flash message?

Step 1: Accessing the link_to helper inside a Rails controller

If you want to access some of the useful helper methods while inside the scope of a controller, you can pull them in with ActionController::Base.helpers. In this example, I wanted to take advantage of link_to and pluralize and interpolate them into a flash message:

# ShoppingListItemBuildersController

def create
  ...
  flash[:notice] = flash_message(ingredient_ids)
  ...
end

private

def flash_message(ingredient_ids)
  pluralized_items = ActionController::Base.helpers.pluralize(ingredient_ids.length, 'item')
  link = ActionController::Base.helpers.link_to(@shopping_list.name.titleize, shopping_list_path(@shopping_list))

  "#{pluralized_items} added to your #{link} list."
end

At this point, we’re half way there. We have a flash message that looks like this:

38 items added to your <a href="/shopping_lists/7">Grocery</a> list.

That’s just HTML and not an actual clickable link. We have a little more work to do.

Step 2: Make the link clickable

In order for the HTML passed into the flash message to be rendered as live HTML and not text, I called the html_safe method on it in my flashes partial.

<!-- app/views/shared/_flashes.html.erb -->

<% flash.each do |type, message| %>
  <div class="flash-notice">
    <%= message.html_safe %>
  </div>
<% end %>

Now, be careful here, like the docs say, “It is your responsibility to ensure that the string contains no malicious content.”