Iterate through events for subscribed entities - AWS SimSpace Weaver

Iterate through events for subscribed entities

Use AllSubscriptionEvents() to get a list of events for subscribed entities (entities in the app's subscription area). The function has the following signature:

Result<SubscriptionChangeList> AllSubscriptionEvents(Transaction& txn)

Then iterate through the entities with a loop, as demonstrated in the following example.

Example
WEAVERRUNTIME_TRY(Api::SubscriptionChangeList subscriptionChangeList, Api::AllSubscriptionEvents(transaction));

for (const Api::SubscriptionEvent& event : subscriptionChangeList.changes)
{
    Api::Entity entity = event.entity;
    Api::ChangeListAction action = event.action;

    switch (action)
    {
    case Api::ChangeListAction::None:
        // insert code to handle the event
        break;
    case Api::ChangeListAction::Remove:
        // insert code to handle the event
        break;
    case Api::ChangeListAction::Add:
        // insert code to handle the event
        break;
    case Api::ChangeListAction::Update:
        // insert code to handle the event
        break;
    case Api::ChangeListAction::Reject:
        // insert code to handle the event
        break;
    }
}
Event types

  • None – The entity is in the area and its position and field data weren't modified.

  • Remove – The entity was removed from the area.

  • Add – The entity was added to the area.

  • Update – The entity is in the area and was modified.

  • Reject – The app failed to remove the entity from the area.

Note

In the case of a Reject event, the app will attempt the transfer again on the next tick.