onCancel property Null safety

(FutureOr<void> Function?()?) onCancel

The callback which is called when the stream is canceled.

May be set to null, in which case no callback will happen.

Implementation

FutureOr<void> Function()? get onCancel;
void onCancel= (FutureOr<void> onCancelHandler())

Implementation

void set onCancel(FutureOr<void> onCancelHandler()?);