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:

1. Add the picker to the model and initialize it in the model init. One message needs to be defined that expects an internal DatePicker message. This is used to update the selection and view of the picker.

import SingleDatePicker as DatePicker

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

type Msg
    = ...
    | UpdatePicker DatePicker.Msg

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

1. We call the DatePicker.view function, passing it the picker Settings and the DatePicker instance to be operated on. The minimal picker Settings only require a Time.Zone

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

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.

1. 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.Msg

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 subMsg ->
            let
                ( newPicker, maybeNewTime ) =
                    SingleDatePicker.update (userDefinedDatePickerSettings model.zone model.currentTime) subMsg model.picker
            in
            ( { 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 needs to happen. To process the DatePicker.Msg you can pass it to the respective DatePicker.update function along with the Settings and the current DatePicker instance. That will then return us the updated DatePicker instance, 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 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 =
    { zone : Zone
    , formattedDay : Weekday -> String
    , formattedMonth : Month -> String
    , isDayDisabled : Zone -> Posix -> Bool
    , focusedDate : Maybe Posix
    , dateStringFn : Zone -> Posix -> String
    , timePickerVisibility : TimePickerVisibility
    , showCalendarWeekNumbers : Bool
    }

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. The styling is based on a CSS-Variables theme that can be easily adjusted for the most important design tokens.