Here’s a tip when using Rails’ button_to and link_to URL helpers!
Never ever forget these two things:

button_to uses the :POST method by default

link_to uses the :GET method by default

Believe me: Memorizing these two simple Rails defaults will save you routing headaches down the road.

Example — Specifying the :GET method:

Let’s say that you’d like to provide your user with a “Cancel” button on a form that redirects her back to the previous page after it’s clicked. (Because you’re nice, you’ll also throw up a warning modal…):

button_to "Cancel / Delete",
          :back,
          confirm: 'Are you sure you would like to cancel and delete this post?',
          disable_with: 'Deleting...'

Guess what? That’s not right! When clicked, that button will either throw a routing error or unintentionally make a post request to one of your routes. Instead, you need to specify that you’d like the button to use the :GET method, instead of its default :POST method. (refer to rule 1 above.)

Here’s the correct code for such a button:

button_to "Cancel / Delete",
          :back,
          method: :get,
          confirm: 'Are you sure you would like to cancel and delete this post?',
          disable_with: 'Deleting...'

See how we specify the method in there with method: :get?

Example — Specifying the :POST method:

Want a text link that ends up sending sending a :POST to one of your routes? Simple. Just remember to pass the correct method:

link_to "Click here to submit post.",
        posts_url,
        method: :post

If you wanted a button to perform the same action, you wouldn’t need to specify the method, as the default method is already :POST:

button_to "Submit Post",
          posts_url,
          disable_with: "Submitting Post...

Example — Specifying the :DELETE method:

Just as you need to pass in the proper HTTP method into your button_to and link_to helpers if you’d like to use them for the opposite of their default method, so too must you specify the :DELETE method when you’d like to use that instead:

button_to "Cancel / Delete",
          :back,
          method: :delete,
          confirm: "Are you sure you'd like to cancel and delete this post?",
          disable_with: "Deleting..."