onBackgroundURLSessionEvents(matching:_:)

Declaration

@MainActor @preconcurrency func onBackgroundURLSessionEvents(matching matchingBlock: ((String) -> Bool)? = nil, _ urlSessionEvent: @escaping (String, @escaping () -> Void) -> Void) -> some WidgetConfiguration

Parameters

• urlSessionEvent:

  A closure that takes a string parameter called identifier and a closure called completion.

Return Value

A widget that triggers urlSessionEvent when events are generated for a URLSession with the specified identifier.

Discussion

When a widget initiates a background network request, the system delivers events related to the request directly to the widget extension instead of the containing app. To process the events, do the following:

1. Use the identifier parameter to determine if a corresponding URLSession object exists. If the system hasn’t terminated your widget extension, maintain a reference to the same URLSession object you used for the original background network request. If the system terminated your widget extension, use the identifier to create a new URLSession object so it can receive the events. You might consider lazily initializing, and caching, the URLSession objects in a central location so that your code works regardless of whether your extension remains active, is suspended, or is terminated.

2. Store a reference to the completion closure to invoke it after the system delivers all events.

3. After the system calls the URLSession delegate’s urlSessionDidFinishEvents(forBackgroundURLSession:) method, invoke the completion closure.