Delay

Elm utilities to trigger updates after a delay

example: https://andrewmacmurray.github.io/elm-delay/

Why?

Sometimes you need to trigger updates after a period of time (i.e. to wait for a css transition or animation to complete) or maybe you need to chain a sequence of these updates (for more complex states).

This library aims for a cleaner way to express this.

How?

Send a single delayed Msg

To trigger a single update after a period of time (in milliseconds) pass Delay.after as a command to the elm runtime:

FirstMessage ->
    model ! [ Delay.after 500 SecondMessage ]

After triggering FirstMessage, 500ms later update will be called with SecondMessage

Send a sequence of delayed Msgs

To send a sequence of Msgs add a new Msg type like so:

type Msg
    = Trigger
    | FirstMessage
    | SecondMessage
    | ThirdMessage
    | Sequence (List (Float, Msg)) -- add this to your Msg type

and add a new branch to your update function like so:

Sequence msgs ->
  Delay.handleSequence Sequence msgs update model

This allows a list of (delay, Msg) to be funnelled to update by passing them as a command to the elm runtime like so:

Trigger ->
    model
        ! [ Delay.start Sequence
                [ ( 1000, FirstMessage )
                , ( 2000, SecondMessage )
                , ( 1000, ThirdMessage )
                ]
          ]

by sending a Trigger Msg:

• after 1000ms update will be called with FirstMessage
• then after 2000ms update will be called with SecondMessage
• then after 1000ms update will be called with ThirdMessage

As a convenience if you'd only like to start a sequence if the model is in a particular shape you can use Delay.startIf

Trigger ->
    model
        ! [ Delay.startIf (not model.updating) Sequence
                [ ( 1000, FirstMessage )
                , ( 2000, SecondMessage )
                , ( 1000, ThirdMessage )
                ]
          ]