How does form_for infer the function to use based on the controller method?

[sweeneydavidj]

In case others come here via search; there is a very informative thread here…

Phoenix form helper and HTTP methods

I have two partials, both get passed an action and a changeset, both start with this code: <%= form_for @changeset, @action, fn f -> %> and then use helper to build inputs. Now as seen above I do not use :method option, though when rendered one of these forms is switched to put: <input name="_method" type="hidden" value="put"> but the other remains post. By (briefly) looking at the form_for as well as to_form and form_tag I didn’t find out what’s going on except that form_tag seems to alr…