Path Helpers and form_for

I have run into an issue when using path helpers in a form_for function when trying to edit a resource. In this case I am trying to update an existing resource.

The router kicks out the following

categories_path  GET        /categories       MyApp.CategoriesController :index
categories_path  POST      /categories       MyApp.CategoriesController :create
categories_path  PATCH   /categories/:id   MyApp.CategoriesController :update
                            PUT       /categories/:id   MyApp.CategoriesController :update

My form_for opens as

<%= form_for(@client_changeset, categories_path(@conn, :update, @client), fn f -> %>

(the categories controller handles submissions for both clients and topics as they are the ‘categories’)

My understanding is, providing a changeset for an existing resource to form_for means the submission would be a POST to

/categories/<id of resource>

with

“_method” => “put” (or “patch”)?

I then take the params where I can use the id for fetching the resource from storage then sending that along with the client params for the update.

However. If I set up the form_for as shown I always get the error,

protocol Enumerable not implemented for %MyApp.Client{... etc }

If I remove the @client from the call to categories_path the error goes away, but the form submission does not include an id in the path.

Revised form_for

<%= form_for(@client_changeset, categories_path(@conn, :update), fn f -> %>

POSTs to

/categories

As a workaround I have added the id @client.id as a hidden field on the form so I can pluck it from the params. This however feels wrong and hacky, and doesn’t align with the boilerplate code a phoenix generator produces or my understanding of the path_helper included in the form_for action.

I’ve checked the categories_path in iex and I can pass

categories_path(MyApp.Endpoint, :update, Repo.get(Client, 1))

and it returns

"/categories/1"

as it should.

Any help here would be greatly appreciated. Thanks.