I'm trying to invoke a process builder process on all Contacts related to an Account, when an Activity (Event) related to that Account is updated.
I know I can update the full set of contact records themselves, for all child Contacts of the Account, using the Update Records action:
Action Type: Update Records
Record Type: [Event].Account ID.Contacts <--this represents all Contacts of the related Account
...but can I pass all the Account's Contacts as the Starting Object(s) for an invoked process? It seems I can only pass a single reference as the Starting Object:
When trying to define the reference for the SObject variable, I navigate a similar UI as when I selected the "Record Type" (record(s) to update) for the Update Records Action, but I can only select parent objects of [Event].Account ID, and [Event].Account ID.Contacts isn't selectable.
I realize I could create a custom "Run Update" field on the Contact object, and update this flag using the Update Records action from the Event-triggered process, then have this Run Update field trigger a process on each Contact record individually, but this seems sloppy. Is there any way to invoke the process on a set of objects like this, without this weird workaround and without Apex?