使用当前日期初始化模型 [英] Initialize model with current date

问题描述

我正在尝试使用当前日期初始化我的模型。我不想使用Native模块。我试图用任务和效果来做。我被困在我的 getCurrentTime 方法。什么是最干净的方式？

I'm trying to initialize my model with the current date. I don't want to use a Native module. I'm trying to do it with Task and Effects. I'm stuck at my getCurrentTime method. What is the cleanest way?

import Time exposing ( Time )
import StartApp
import Task
import Effects exposing (Never)
import Html exposing ( Html )

app = 
  StartApp.start
    { init = init
    , view = view
    , update = update
    , inputs = []}

main = 
  app.html

port tasks : Signal (Task.Task Never ())
port tasks =
  app.tasks

type alias Model = 
    { clock : Time}

init : (Model, Effects.Effects Action)
init = ((Model  ), Effects.none)

type Action = ShowClock 

update : Action -> Model -> (Model, Effects.Effects Action)
update action model = 
  case action of
    ShowClock c -> 
      ({ model | clock = c}, Effects.none)

getCurrentTime : Effects.Effects Action
getCurrentTime =
  -- stuck here
  |> Task.map ShowClock
  |> Effects.task

view : Signal.Address Action -> Model -> Html
view address model =
  Signal.map Html.text model.clock

It would also be nice to convert the time to a string with "YYYY-MM-DD" format.

推荐答案

一个ELM包可从 http：//package.elm- lang.org/packages/evancz/task-tutorial/1.0.3/TaskTutorial ，可以用来获取当前时间。

There is an ELM package available at http://package.elm-lang.org/packages/evancz/task-tutorial/1.0.3/TaskTutorial you can use to get the current time.

首先你需要下载它使用终端或Windows命令中的以下命令更新您的elm-package.json文件：

First you need to download it and update your elm-package.json file using the following command in a terminal or Windows command:

elm-package install evancz/task-tutorial 1.0.3

然后更新你的代码：

getCurrentTime : Effects.Effects Action
getCurrentTime = Effects.task <| Task.map ShowClock ( TaskTutorial.getCurrentTime )

最后，你只需要调用getCurrentTime作为一个特效您的模型将被更新。

Finally, you just have to call getCurrentTime as an Effects Action and your model will be updated.

将您的时间转换为人类可读的日期String可以使用此小帮助函数：

To convert your Time into a human readable date String you can use this little helper function:

 toHRDate : Time -> String -- to human readable date
 toHRDate t =
     let
       date = Date.fromTime t
       d = toString (Date.day date) -- day
       m = toString (Date.month date) -- month
       y = toString (Date.year date) -- year
       hrd = d ++ "-" ++ m ++ "-" ++ y
    in hrd

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