I have a function below and when I link with the iOS 11 SDK, I get an error:
Do not add subviews directly to the visual effect view itself, instead ad
Apple says that;
Depending on the desired effect, the effect may affect content layered behind the view or content added to the visual effect view’s contentView. Apply a visual effect view to an existing view and then apply a UIBlurEffect or UIVibrancyEffect object to apply a blur or vibrancy effect to the existing view. After you add the visual effect view to the view hierarchy, add any subviews to the contentView property of the visual effect view. Do not add subviews directly to the visual effect view itself.
So, as per @the4kman add your subviews to content view of visual effect view
effectView.contentView.addSubview(activityIndicator)
effectView.contentView.addSubview(strLabel)