copy routing with useElmish to V5 recipes

docs/recipes/ui/routing-with-elmish.md

@@ -0,0 +1,289 @@
+# How do I create multi-page applications with routing and the useElmish hook?
+
+[UseElmish](https://zaid-ajaj.github.io/Feliz/#/Hooks/UseElmish) is a powerful package that allows you to write standalone components using Elmish. A component built around the `UseElmish` hook has its own view, state and update function.
+
+In this recipe we add routing to a safe app, and implement the todo list page using the `UseElmish` hook.
+
+## 1. Installing dependencies
+
+Install Feliz.Router in the Client project
+
+```bash
+dotnet paket add Feliz.Router -p Client
+```
+
+Install Feliz.UseElmish in the Client project
+
+```bash
+cd src/Client
+dotnet femto install Feliz.UseElmish
+```
+
+Open the router in the client project
+
+```fsharp title="Index.fs"
+open Feliz.Router
+```
+
+## 2. Extracting the todo list module
+
+Create a new Module `TodoList` in the client project. Move the following functions and types to the TodoList Module:
+
+* Model
+* Msg
+* todosApi
+* init
+* todoAction
+* todoList
+
+Also open `Shared`, `Fable.Remoting.Client`, `Elmish` and `Feliz`. 
+
+```fsharp title="TodoList.fs"
+module TodoList
+
+open Shared
+open Fable.Remoting.Client
+open Elmish
+
+open Feliz
+
+type Model = { Todos: Todo list; Input: string }
+
+type Msg =
+    | GotTodos of Todo list
+    | SetInput of string
+    | AddTodo
+    | AddedTodo of Todo
+
+let todosApi =
+    Remoting.createApi ()
+    |> Remoting.withRouteBuilder Route.builder
+    |> Remoting.buildProxy<ITodosApi>
+
+let init () =
+    let model = { Todos = []; Input = "" }
+    let cmd = Cmd.OfAsync.perform todosApi.getTodos () GotTodos
+    model, cmd
+
+let update msg model =
+    match msg with
+    | GotTodos todos -> { model with Todos = todos }, Cmd.none
+    | SetInput value -> { model with Input = value }, Cmd.none
+    | AddTodo ->
+        let todo = Todo.create model.Input
+
+        let cmd = Cmd.OfAsync.perform todosApi.addTodo todo AddedTodo
+
+        { model with Input = "" }, cmd
+    | AddedTodo todo ->
+        {
+            model with
+                Todos = model.Todos @ [ todo ]
+        },
+        Cmd.none
+
+let private todoAction model dispatch =
+    Html.div [
+        prop.className "flex flex-col sm:flex-row mt-4 gap-4"
+        prop.children [
+            Html.input [
+                prop.className
+                    "shadow appearance-none border rounded w-full py-2 px-3 outline-none focus:ring-2 ring-teal-300 text-grey-darker"
+                prop.value model.Input
+                prop.placeholder "What needs to be done?"
+                prop.autoFocus true
+                prop.onChange (SetInput >> dispatch)
+                prop.onKeyPress (fun ev ->
+                    if ev.key = "Enter" then
+                        dispatch AddTodo)
+            ]
+            Html.button [
+                prop.className
+                    "flex-no-shrink p-2 px-12 rounded bg-teal-600 outline-none focus:ring-2 ring-teal-300 font-bold text-white hover:bg-teal disabled:opacity-30 disabled:cursor-not-allowed"
+                prop.disabled (Todo.isValid model.Input |> not)
+                prop.onClick (fun _ -> dispatch AddTodo)
+                prop.text "Add"
+            ]
+        ]
+    ]
+
+[<ReactComponent>]
+let todoList model dispatch =
+    Html.div [
+        prop.className "bg-white/80 rounded-md shadow-md p-4 w-5/6 lg:w-3/4 lg:max-w-2xl"
+        prop.children [
+            Html.ol [
+                prop.className "list-decimal ml-6"
+                prop.children [
+                    for todo in model.Todos do
+                        Html.li [ prop.className "my-1"; prop.text todo.Description ]
+                ]
+            ]
+
+            todoAction model dispatch
+        ]
+    ]
+```
+
+## 4. Add the UseElmish hook to the TodoList view function
+
+open Feliz.UseElmish in the TodoList Module
+
+```fsharp title="TodoList.fs"
+open Feliz.UseElmish
+...
+```
+
+In the todoList module, rename the function `todoList` to `view`, and remove the `private` access modifier.
+On the first line, call `React.useElmish`, passing it the `init` and `update` functions. Bind the output to `model` and `dispatch`
+
+=== "Code"
+    ```fsharp title="TodoList.fs"
+    let view model dispatch =
+        let model, dispatch = React.useElmish (init, update, [||])
+        ...
+    ```
+
+=== "Diff"
+    ```.diff title="TodoList.fs"
+    -let containerBox model dispatch =
+    +let view model dispatch =
+    +    let model, dispatch = React.useElmish (init, update, [||])
+        ...
+    ```
+
+Replace the arguments of the function with unit, and add the `ReactComponent` attribute to it
+
+=== "Code"
+    ```fsharp title="Index.fs"
+    [<ReactComponent>]
+    let view () =
+        ...
+    ```
+=== "Diff"
+    ```.diff title="Index.fs"
+    + [<ReactComponent>]
+    - let view model dispatch =
+    + let view () =
+          ...
+    ```
+
+## 5. Add a new model to the Index module
+
+In the `Index module`, create a model that holds the current page
+
+```fsharp title="Index.fs"
+type Page =
+    | TodoList
+    | NotFound
+
+type Model =
+    { CurrentPage: Page }
+```
+## 6. Initializing the application
+
+Create a function that initializes the app based on an url
+
+```fsharp title="Index.fs"
+let initFromUrl url =
+    match url with
+    | [ "todo" ] ->
+        let model = { CurrentPage = TodoList }
+
+        model, Cmd.none
+    | _ ->
+        let model = { CurrentPage = NotFound }
+
+        model, Cmd.none
+```
+
+Create a new `init` function, that fetches the current url, and calls initFromUrl. 
+
+```fsharp title="Index.fs"
+let init () = Router.currentUrl () |> initFromUrl
+```
+## 7. Updating the Page
+
+Add a `Msg` type, with an PageChanged case
+
+```fsharp title="Index.fs"
+type Msg = 
+    | PageChanged of string list
+```
+Add an `update` function, that reinitializes the app based on an URL
+
+```fsharp title="Index.fs"
+let update msg model =
+    match msg with
+    | PageChanged url -> initFromUrl url
+```
+
+## 8. Displaying pages
+
+Add a pageContent function to the `Index` module, that returns the appropriate page content
+
+```fsharp title="Index.fs"
+let pageContent model =
+    match model.CurrentPage with
+    | NotFound -> Html.text "Page not found"
+    | TodoList -> TodoList.view ()
+```
+
+In the `view` function, replace the call to `todoList` with a call to `pageContent`
+
+=== "Code"
+    ```fsharp title="Index.fs"
+    let view model dispatch =
+        Html.section [
+            ...
+            pageContent model
+            ...
+        ]
+    ```
+=== "Diff"
+    ```diff title="Index.fs"
+     let view model dispatch =
+         Html.section [
+         ...
+     -   todoList view model
+     +   pageContent model
+         ...
+         ]
+    ```
+
+## 9. Add the router to the view
+
+Wrap the content of the view method in a `React.Router` element's router.children property, and add a `router.onUrlChanged` property to dispatch the urlChanged message
+
+=== "Code"
+    ```fsharp title="Index.fs"
+    let view model dispatch =
+        React.router [
+            router.onUrlChanged ( PageChanged>>dispatch )
+            router.children [
+                Html.section [
+                ...
+                ]
+            ]
+        ]
+    ```
+=== "Diff"
+    ```diff title="Index.fs"
+    let view (model: Model) (dispatch: Msg -> unit) =
+    +   React.router [
+    +       router.onUrlChanged ( PageChanged>>dispatch )
+    +       router.children [
+                Html.section [
+                ...
+                ]
+    +       ]
+    +   ]
+    ```
+
+## 10.  Try it out
+
+The routing should work now. Try navigating to [localhost:8080](http://localhost:8080/); you should see a page with "Page not Found". If you go to [localhost:8080/#/todo](http://localhost:8080/#/todo), you should see the todo app.
+
+!!! info "# sign"
+    You might be surprised to see the hash sign as part of the URL. It enables React to react to URL changes without a full page refresh.
+    There are ways to omit this, but getting this to work properly is outside of the scope of this recipe.

mkdocs.yml

@@ -86,6 +86,7 @@ nav:
           - Migrate from a CDN stylesheet to an NPM package: "recipes/ui/cdn-to-npm.md"
           - Add routing with state shared between pages: "recipes/ui/add-routing.md"
           - Add routing with separate models per page: "recipes/ui/add-routing-with-separate-models.md"
+          - Add Routing with UseElmish: "recipes/ui/routing-with-elmish.md"
       - Storage:
           - Quickly add a database: "recipes/storage/use-litedb.md"
       - JavaScript: