In Sketch 3.8, we introduced the Action API: a way to let plugins react to events in the app. Using it, plugin authors can write code that is executed when certain actions are triggered, like “opening a document”, “saving”, “adding an artboard”…

What is an action?

An action is an event that happens in the app, usually as a consequence of a user interaction. Actions have names like CloseDocument, DistributeHorizontally or TogglePresentationMode, and you can tell your plugin to run bits of code when those actions are triggered.

How do I register my plugin to “listen” for an action?

Easy: you just add a handler in the manifest.json file that your plugin already has.

We’re going to add a new handler, for the OpenDocument action:

"commands" : [
+  {
+    "script" : "my-action-listener.js",
+    "name" : "My Action Listener",
+    "handlers" : {
+      "actions": {
+        "OpenDocument": "onOpenDocument"
+      }
+    },
+    "identifier" : "my-action-listener-identifier"
+  }

We’re telling our plugin that we want to run the onOpenDocument function when a document is open, so let’s add that in my-action-listener.js:

export function onOpenDocument(context) {
  context.actionContext.document.showMessage('Document Opened')

Save everything, build the plugin and now whenever you open a document in Sketch you should see a small toast banner saying “Document Opened”.

Action Contexts

When an action is triggered, Sketch can send the target function some information about the action itself (like the selected layers when the selection changes, or the current document when a new document is open). We call that the Action Context, and you can access it from the context that is sent as a parameter of the target function using context.actionContext.

Keep in mind, though, that not all actions set an Action Context yet. In fact, most of them don’t at the moment, so if you think there’s something you’d like to access in an Action Context, send us a note and we’ll add it as soon as possible.

begin/finish actions

Some actions (like SelectionChanged) actually happen in two phases: begin and finish. If you want to call a function only on one of them, you can add a handler for SelectionChanged.begin, or SelectionChanged.finish. If you don’t add anything, the action will be triggered twice.

Finding the right action

For a list of all the available actions in the API, check the Actions Reference section.

Pro Tip: sometimes browsing the list is too much work, and you just want something a bit more direct. For those cases, you can listen to all the actions to find the one you need.

Again, if there’s any event you’d like to see added to the list, let us know and we’ll try to add it (some events are not on the list for performance reasons, like “layer is dragged”).

Next steps

If you’d like to read more generally about the Action API, try these topics:

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