The basics of workflow app interactivity

Adding interactivity to your app adds a dynamic experience that makes it more substantive than just a bot sending messages. There are a few different ways to achieve interactivity in a workflow app.

  1. Collect user input through a form and use it later in the workflow.
  2. Create an interactive message with varying options of back-and-forth with the user.
  3. Use interactive modals to ask your users questions, allow actions, and update based on the information they give you.

Basic elements of interactivity

All options share some basic elements in common.

  • Interactivity parameter
  • Blocks with interactive parts
  • Interactivity handlers

Interactivity parameter

In order to prevent inundating users with pop-ups they didn't ask for, all app interactivity requires an interactivity parameter. This is the user's consent to interact with the app; only a user's interaction can open a form or modal.

Whether the user is opening a form, modal, or sending an interactive message, this looks the same—including an input_parameter of the type interactivity.

Not supported in Workflow Builder
Custom functions that require interactivity inputs are not currently supported in Workflow Builder.

Interactive blocks

Both modals and interactive messages allow for interactive blocks, a flexible and dynamic way to create visually appealing app interaction. Check out an example in step 2 of Creating an interactive message, explore the Block Kit reference for a menu of interactive options, then try them out in Block Kit Builder.

Interactivity handlers

An interactive form is a static mechanism that merely gathers information from the user, but modals and messages allow for more of a back-and-forth interaction. This means being able to respond to your user's actions and inputs dynamically. This is achieved by utilizing interactivity handlers.

Handler name Description Where it can be used
BlockActionsHandler Used to respond to interactivity that happens within an interactive block. Messages Modals
BlockSuggestionHandler Used alongside a select menu of external data source element. Messages Modals
ViewSubmissionHandler Used to update a modal view after it has been submitted. Modals
ViewClosedHandler Used to update an app after a view has been closed. Modals
UnhandledEventHandler Used as a catch-all for unhandled events. Messages Modals

It's best practice to properly handle a function's success or error when a modal is submitted or closed. Refer to creating an interactive modal for more details.

View sample payloads for these handlers in the Interaction payloads documentation.

Invoking interactivity handlers

Each handler contains two arguments, a constraint and a handler, such that its invocation will look like this:

  • addBlockActionsHandler(constraint, handler)
  • addBlockSuggestionHandler(constraint, handler)
  • addViewSubmissionHandler(constraint, handler)
  • addViewClosedHandler(constraint, handler)
  • addUnhandledEventHandler(constraint, handler)

If any incoming event matches the constraint, the specified handler will be invoked with the event payload. The handler arugment is the handler function that you define—what you want to happen in this event. Every type of handler function has the same context properties available to it, which are the same as the context properties available to custom functions. This allows for authoring focused, single-purpose handlers and provides a concise, yet flexible API for registering handlers to specific interactions.

What the constraint field allows depends on the type of handler.

Block actions and block suggestions

For the BlockActionsHandler and the BlockSuggestionHandler, the constraint can be either a BlockActionConstraintField or a BlockActionConstraintObject.

BlockActionConstraintField can be one of three options.

type BlockActionConstraintField = string | string[] | RegExp;
  • When provided as a string, it must match the field exactly.
  • When provided as an array of string, it must match one of the array values exactly.
  • When provided as a RegExp, the regular expression must match.

The BlockActionConstraintObject contains two properties.

type BlockActionConstraintObject = {
  block_id?: BlockActionConstraintField;
  action_id?: BlockActionConstraintField;
};

When the constraint is provided as an object in the form of a BlockActionConstraintObject, it can contain either or both a block_id and an action_id.

  • Each of these properties is a BlockActionConstraintField (see above).
  • If both the action_id and block_id properties exist on the constraint, then both action_id and block_id properties must match any incoming action.
  • If only one of these properties is provided, then only the provided property must match.

See an example of the BlockActionsHandler and the BlockSuggestionHandler in action in the Creating an interactive message guide.

View handlers

The constraint field for the view handlers is a bit different than in the BlockActionsHandler and BlockSuggestionHandler.

SlackFunction({ ... }).addViewSubmissionHandler("my_view_callback_id", async (ctx) => { ... });

For view handlers, the consraint argument can be either a string, string[], or a RegExp.

  • A simple string constraint must match a view's callback_id exactly.
  • A string [] constraint must match a view's callback_id to any of the strings in the array.
  • A regular expression constraint must match a view's callback_id.

Unhandled handlers

The UnhandledEventHandler handles everything unaccounted for. It then makes sense that this handler does not accept a constraint argument. It does, however, accept the same handler argument as the other handlers, which is the handler function you define. Remember, all custom function context properties are availalbe for use here.


.addUnhandledEventHandler(({ body: _body }) => {
    console.log("unhandled event happened");
    //add some other actions
  })

Next steps

Ready to get started?

✨ Get started with collecting user input by creating a form.

✨ Dazzle your users by sending them an interactive message.

✨ Create some back-and-forth banter with interactive modals.

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