upgrade-2-to-3.md

Upgrading from 2 to 3

Hop has changed in many ways in version 3. Please review the Getting started guide. Following is an overview of the major changes.

Routes

Now routes can take values, instead of:

type Route
  = Home
  | Users
  | User
  | Token

You can have values attached:

type Route
  = Home
  | Users
  | User Int
  | Token String

Routes are now defined using matchers. So instead of

routes =
  [ ("/users/:int", User) ]

You do:

import Hop.Matchers exposing(match2)

userMatcher =
  match2 User "/users/" int

matchers =
  [userMatcher]

This is so we can have stronger types e.g. User Int.

Actions

Hop.signal now returns a tuple with (Route, Location). Your application needs to map this to an action. e.g.

type Action
  = HopAction ()
  | ApplyRoute ( Route, Location )

taggedRouterSignal : Signal Action
taggedRouterSignal =
  Signal.map ApplyRoute router.signal

This is so routes (Route) are different type than the application actions.

Payload

Before Hop returned a payload with a dictionary with matched parameters.

Now it returns the matched route with the values e.g. User 1 and a Location record in the form of a tuple:

(User 1, location)

location has the information about the current path and the query:

{
  path = ["users", "1"],
  query = <Dict String String>
}

Views

In your views you don't need to 'search' for the correct parameter in the payload anymore. The parameters are now in the route e.g. User 1.

So instead of doing:

userId =
  model.routerPayload.params
    |> Dict.get "userId"
    |> Maybe.withDefault ""

You simply get the id from the route:

case User userId ->
  ...

The query is still a dictionary. The query is now in the location record as shown above.