pow

Defintion of succeess

• On Time
• On Budget
• Users Are Happy

Setting Expectations // Common language

Elm

Counter Example

module Counter where

import Html exposing (..)
import Html.Events exposing (onClick)

-- MODEL

type alias Model = Int

init : Int -> Model
init count = count

-- UPDATE

type Action = Increment | Decrement

update : Action -> Model -> Model
update action model =
  case action of
    Increment -> model + 1
    Decrement -> model - 1

-- VIEW

view : Signal.Address Action -> Model -> Html
view address model =
  div []
    [ button [ onClick address Decrement ] [ text "-" ]
    , div [] [ text (toString model) ]
    , button [ onClick address Increment ] [ text "+" ]
    ]

No Side Effects

type alias Model = Int

type Action
 = GetDataFromServer
 | UpdateDataFromServer Result

GetDataFromServer ->
 ( model, Http.get "https://example.com/api/data" |> Task.map UpdateDataFromServer )

UpdateDataFromServer result ->
 case result of
   Ok val ->
     ( { model = val } , Effects.none )
   Err msg ->
     ( model , Effects.none )

port dropzoneUploadedFile : Signal (Maybe Int)

dropZone = new Dropzone();

dropZone.on('complete', function(response) {
 var id = parseInt(response.id);
 elmApp.ports.dropzoneUploadedFile.send(id);
});

Unit Testing

update : Action -> Model -> Model
update action model =
  case action of
    Increment -> model + 1
    Decrement -> model - 1

[ test "negative count" (assertEqual 0 (update Increment -1))
, test "zero count"     (assertEqual 1 (update Increment  0))
, test "positive count" (assertEqual 2 (update Increment  1))
]

Elm // PowToon