Disclaimer: I hope all of this is accurate, and not the result of some stupid typo I failed to notice. Anyways…

This post comprises 2 issues in the same section “The Promo Live View”. The first issue is relatively minor, but the second issue required some digging to fix:

1. The PDF e-book contains an image on page 132 that shows a basic promo page in the browser (ie. no form is visible). However, the code sample on the previous page contains a <.simple_form> Live Component which will not properly render until after the code below the aforementioned image has been added. I am guessing the intention was to show the basic rendered page before adding the form component. By adding the code snippet on page 132, the issue is resolved. No big deal. However, another issue arose as I continued…

2. On page 133, the code snippet presents <.simple_form> component contains an <.input> component that binds the field attribute as follows:

<.input field={{f, :first_name}} type="text" label="First name" />
<.input field={{f, :email}} type="email" label="Email address" phx-debounce="blur" />

However, when using Phoenix ~> 1.7.3 and LiveView ~> 0.19.0, this results in the following error:

key :name not found in: %{
  id: nil,
  label: "First name",
  type: "text",
  prompt: nil,
  field: {%Phoenix.HTML.Form{
     source: #Ecto.Changeset<
       action: nil,
       changes: %{},
       errors: [
         first_name: {"can't be blank", [validation: :required]},
         email: {"can't be blank", [validation: :required]}
       ],
       data: #Pento.Promo.Recipient<>,
       valid?: false
     >,
     impl: Phoenix.HTML.FormData.Ecto.Changeset,
     id: "promo-form",
     name: "recipient",
     data: %Pento.Promo.Recipient{first_name: nil, email: nil},
     hidden: [],
     params: %{},
     errors: [],
     options: [
       method: "post",
       id: "promo-form",
       multipart: false,
       "phx-change": "validate",
       "phx-submit": "save"
     ],
     index: nil,
     action: nil
   }, :first_name},
  errors: [],
  rest: %{},
  multiple: false,
  __changed__: nil,
  __given__: %{
    label: "First name",
    type: "text",
    field: {%Phoenix.HTML.Form{
       source: #Ecto.Changeset<
         action: nil,
         changes: %{},
         errors: [
           first_name: {"can't be blank", [validation: :required]},
           email: {"can't be blank", [validation: :required]}
         ],
         data: #Pento.Promo.Recipient<>,
         valid?: false
       >,
       impl: Phoenix.HTML.FormData.Ecto.Changeset,
       id: "promo-form",
       name: "recipient",
       data: %Pento.Promo.Recipient{first_name: nil, email: nil},
       hidden: [],
       params: %{},
       errors: [],
       options: [
         method: "post",
         id: "promo-form",
         multipart: false,
         "phx-change": "validate",
         "phx-submit": "save"
       ],
       index: nil,
       action: nil
     }, :first_name},
    __changed__: nil
  },
  inner_block: []
}

I made a couple small changes to get things working:

lib/pento_web/live/promo_live.html.heex (Modify the <.input> components)

  <.input field={f[:first_name]} type="text" label="First name" phx-debounce="500" />
  <.input field={f[:email]} type="email" label="Email address" phx-debounce="blur" />

I took inspiration for these changes by copying from the LiveView docs.

However, a different section of the same docs page suggests that the current approach taken by the book is discouraged and that a different approach should be used. I’m looking into this now (and I’m way out of my league… I am not up to snuff on using forms in Phoenix/LV) and will suggest a revised approach if I can 1) figure it out, and 2) get it working with the process described in the book.