Static AVCaptureSessionErrorKey 

pub unsafe static AVCaptureSessionErrorKey: &'static NSString

Available on crate feature AVCaptureSession only.

The key used to provide an NSError describing the failure condition in an AVCaptureSessionRuntimeErrorNotification.

AVCaptureSessionErrorKey may be found in the userInfo dictionary provided with an AVCaptureSessionRuntimeErrorNotification. The NSError associated with the notification gives greater detail on the nature of the error, and in some cases recovery suggestions.

See also Apple’s documentation