Update part8 and part9

part8/ElmHub.elm

@@ -1,18 +1,19 @@
 module ElmHub (..) where
 
 import Html exposing (..)
-import Html.Attributes exposing (..)
+import Html.Attributes exposing (class, target, href, property)
 import Html.Events exposing (..)
 import Http
 import Auth
 import Task exposing (Task)
 import Effects exposing (Effects)
 import Json.Decode exposing (Decoder, (:=))
+import Json.Decode.Pipeline exposing (..)
 import Json.Encode
 import Signal exposing (Address)
 
 
-searchFeed : Address String -> String -> Task x Action
+searchFeed : Address String -> String -> Effects Action
 searchFeed address query =
   let
     -- See https://developer.github.com/v3/search/#example for how to customize!
@@ -23,13 +24,15 @@ searchFeed address query =
         ++ query
         ++ "+language:elm&sort=stars&order=desc"
 
-    -- These only talk to JavaScript ports now. They don't
+    -- These only talk to JavaScript ports now. They never result in Actions
     -- actually do any actions themselves.
     task =
-      Signal.send address query
-        |> Task.map (\_ -> DoNothing)
+      performAction
+        (\_ -> DoNothing)
+        (\_ -> DoNothing)
+        (Signal.send address query)
   in
-    Task.onError task (\_ -> Task.succeed DoNothing)
+    Effects.task task
 
 
 responseDecoder : Decoder (List SearchResult)
@@ -39,16 +42,40 @@ responseDecoder =
 
 searchResultDecoder : Decoder SearchResult
 searchResultDecoder =
-  Json.Decode.object3
-    SearchResult
-    ("id" := Json.Decode.int)
-    ("full_name" := Json.Decode.string)
-    ("stargazers_count" := Json.Decode.int)
+  decode SearchResult
+    |> required "id" Json.Decode.int
+    |> required "full_name" Json.Decode.string
+    |> required "stargazers_count" Json.Decode.int
+
+
+{-| Note: this will be a standard function in the next release of Elm.
+
+Example:
+
+
+type Action =
+  HandleResponse String | HandleError Http.Error
+
+
+performAction
+  (\responseString -> HandleResponse responseString)
+  (\httpError -> HandleError httpError)
+  (Http.getString "https://google.com?q=something")
+
+-}
+performAction : (a -> b) -> (y -> b) -> Task y a -> Task x b
+performAction successToAction errorToAction task =
+  let
+    successTask =
+      Task.map successToAction task
+  in
+    Task.onError successTask (\err -> Task.succeed (errorToAction err))
 
 
 type alias Model =
   { query : String
   , results : List SearchResult
+  , errorMessage : Maybe String
   }
 
 
@@ -67,6 +94,7 @@ initialModel : Model
 initialModel =
   { query = "tutorial"
   , results = []
+  , errorMessage = Nothing
   }
 
 
@@ -81,12 +109,23 @@ view address model =
         ]
     , input [ class "search-query", onInput address SetQuery, defaultValue model.query ] []
     , button [ class "search-button", onClick address Search ] [ text "Search" ]
+    , viewErrorMessage model.errorMessage
     , ul
         [ class "results" ]
         (List.map (viewSearchResult address) model.results)
     ]
 
 
+viewErrorMessage : Maybe String -> Html
+viewErrorMessage errorMessage =
+  case errorMessage of
+    Just message ->
+      div [ class "error" ] [ text message ]
+
+    Nothing ->
+      text ""
+
+
 onInput address wrap =
   on "input" targetValue (\val -> Signal.message address (wrap val))
 
@@ -114,6 +153,7 @@ type Action
   | SetQuery String
   | DeleteById ResultId
   | SetResults (List SearchResult)
+  | SetErrorMessage (Maybe String)
   | DoNothing
 
 
@@ -121,17 +161,16 @@ update : Address String -> Action -> Model -> ( Model, Effects Action )
 update searchAddress action model =
   case action of
     Search ->
-      ( model, Effects.task (searchFeed searchAddress model.query) )
+      ( model, searchFeed searchAddress model.query )
 
     SetQuery query ->
       ( { model | query = query }, Effects.none )
 
     SetResults results ->
-      let
-        newModel =
-          { model | results = results }
-      in
-        ( newModel, Effects.none )
+      ( { model | results = results }, Effects.none )
+
+    SetErrorMessage errorMessage ->
+      ( { model | errorMessage = errorMessage }, Effects.none )
 
     DeleteById idToHide ->
       let

part8/Main.elm

@@ -20,7 +20,7 @@ app =
   StartApp.start
     { view = view
     , update = update search.address
-    , init = ( initialModel, Effects.task (searchFeed search.address initialModel.query) )
+    , init = ( initialModel, searchFeed search.address initialModel.query )
     , inputs = [ responseActions ]
     }
 
@@ -47,12 +47,11 @@ responseActions =
 
 decodeGithubResponse : Json.Encode.Value -> Action
 decodeGithubResponse value =
-  case Json.Decode.decodeValue responseDecoder value of
-    Ok results ->
-      SetResults results
-
-    Err _ ->
-      DoNothing
+  -- TODO use Json.Decode.DecodeValue to decode the response into an Action.
+  --
+  -- Hint: look at ElmHub.elm, specifically the definition of Action and
+  -- the deefinition of responseDecoder
+  SetErrorMessage (Just "TODO decode the response!")
 
 
 port githubResponse : Signal Json.Encode.Value

part8/elm-package.json

@@ -4,10 +4,12 @@
     "repository": "https://github.com/rtfeldman/elm-workshop.git",
     "license": "BSD-3-Clause",
     "source-directories": [
-        ".", ".."
+        ".",
+        ".."
     ],
     "exposed-modules": [],
     "dependencies": {
+        "NoRedInk/elm-decode-pipeline": "1.0.0 <= v < 2.0.0",
         "elm-lang/core": "3.0.0 <= v < 4.0.0",
         "evancz/elm-effects": "2.0.0 <= v < 3.0.0",
         "evancz/elm-html": "4.0.0 <= v < 5.0.0",
@@ -15,4 +17,4 @@
         "evancz/start-app": "2.0.0 <= v < 3.0.0"
     },
     "elm-version": "0.16.0 <= v < 0.17.0"
-}
+}