elm-datetime-picker

Single and duration datetime picker components written in Elm 0.19

Install

elm install mercurymedia/elm-datetime-picker

In action

Single Picker

Duration Picker

Usage

This package exposes two modules SingleDatePicker and DurationDatePicker. As their names imply, SingleDatePicker can be used to pick a singular datetime while DurationDatePicker is used to select a datetime range. To keep things simple, the documentation here focuses on the SingleDatePicker but both types have an example app for additional reference.

There are four steps to configure the DatePicker:

Add the picker to the model and initialize it in the model init

import SingleDatePicker as DatePicker

type alias Model =
    { ...
    , picker : DatePicker.DatePicker
    }

init : ( Model, Cmd Msg )
init =
    ( { ...
      , picker = DatePicker.init
      }
    , Cmd.none
    )

One message needs to be defined that expects an updated DatePicker instance as well as a Maybe Posix representing a datetime selection. This message is added to the picker settings along with a Zone.

type Msg
    = ...
    | UpdatePicker ( DatePicker.DatePicker, Maybe Posix )

userDefinedDatePickerSettings : Zone -> DatePicker.Settings Msg
userDefinedDatePickerSettings timeZone =
    DatePicker.defaultSettings timeZone UpdatePicker

We call the DatePicker.view function, passing it the defined settings and the DatePicker instance to be operated on. Because the messages for handling picker updates are defined in the calling module and passed in via the settings, we do not need to worry about Html.mapping!

view : Model -> Html Msg
view model =
    ...
    div []
        [ button [ onClick OpenPicker ] [ text "Open Me!" ]
        , DatePicker.view userDefinedDatePickerSettings model.picker
        ]

While we are on the topic of the DatePicker.view, it is worth noting that this date picker does not include an input or button to trigger the view to open, this is up to the user to define and allows the picker to be flexible across different use cases.

Now it is time for the meat and potatoes: handling the DatePicker updates, including saving the time selected in the picker to the calling module's model.

type alias Model =
    { ...
    , today : Posix
    , zone : Zone
    , pickedTime : Maybe Posix
    , picker : DatePicker.DatePicker
    }

type Msg
    = ...
    | OpenPicker
    | UpdatePicker ( DatePicker.DatePicker, Maybe Posix )

update : Msg -> Model -> ( Model, Cmd Msg )
update msg model =
    case msg of
        ...

        OpenPicker ->
            ( { model | picker = DatePicker.openPicker model.zone model.today model.pickedTime model.picker }, Cmd.none )

        UpdatePicker ( newPicker, maybeNewTime ) ->
            ( { model | picker = newPicker, pickedTime = Maybe.map (\t -> Just t) maybeNewTime |> Maybe.withDefault model.pickedTime }, Cmd.none )

The user is responsible for defining his or her own Open picker message and placing the relevant event listener where he or she pleases. When handling this message in the update as seen above, we call DatePicker.openPicker which simply returns an updated picker instance to be stored on the model (DatePicker.closePicker is also provided and returns an updated picker instance like openPicker does). DatePicker.openPicker takes a Zone (the time zone in which to display the picker), Posix (the base time), a Maybe Posix (the picked time), and the DatePicker instance we wish to open. The base time is used to inform the picker what day it should center on in the event no datetime has been selected yet. This could be the current date or another date of the implementer's choosing.

Remember that message we passed into the DatePicker settings? Here is where it comes into play. UpdatePicker let's us know that an update of the DatePicker instance's internal state has occured. Seeing as we don't need to do any additional processing here, the UpdatePicker message simply carries the updated DatePicker instance along with it to save in the model of the calling module. Additionally, we get a Maybe Posix. In the case of Just a time, we set that on the model as the new pickedTime otherwise we default to the current pickedTime.

Automatically close the picker

In the event you want the picker to close automatically when clicking outside of it, the module uses a subscription to determine when to close (outside of a save). Wire the picker subscription like below.

subscriptions : Model -> Sub Msg
subscriptions model =
    SingleDatePicker.subscriptions UpdatePicker model.picker

Additional Configuration

This is the settings type to be used when configuring the datepicker. More configuration will be available in future releases.

type alias Settings msg =
    { formattedDay : Weekday -> String
    , formattedMonth : Month -> String
    , focusedDate : Maybe Posix
    , dayDisabled : Posix -> Bool
    , internalMsg : ( DatePicker, Maybe Posix ) -> msg
    }

Examples

Examples can be found in the examples folder. To build the examples to view in the browser run: cd examples && make && cd .. from the root of the repository.

CSS

The CSS for the date picker is distributed separately and can be found here

PaackEng/elm-datetime-picker