Page.component

pages that make global updates.

pages that make global updates.

A "component" page is just a Page.element that can update the global state by sending messages!

Both init and update now return something like this:

( Model, Cmd Msg, Cmd Global.Msg )

We can use elm-spa add to create a component page like this:

elm-spa add component SignIn

A sign in page is a good example of when we would reach for a component instead of an element.

We can have the update function send out a Global message to update the logged in user.

It's also very common to omit the always to give our functions access to the Global.Model from the page context.

Page.component
  { title = always title
  , init = init -- *removed always
  , update = update -- *removed always
  , view = view -- *removed always
  , subscriptions = always subscriptions
  }

Maybe your init does something like this:

import Global

type alias Model =
  { user : Maybe User
  }

type Msg = NoOp

init :
  PageContext
  -> Params.SignIn
  -> ( Model, Cmd Msg, Cmd Global.Msg )
init context _ =
  ( { user = context.global.user }
  , Cmd.none
  , Global.SignIn "ryan@elm-spa.dev"
  )