Returns an identifier object used to track the progress of loading a single resource.
- macOS 10.2–10.14Deprecated
The web view that sent this message.
The request that initiated this load for
The data source for this web view.
An identifier object that is retained by
sender and passed as a parameter to all other delegate messages pertaining to this resource.
Delegates might implement this method to begin tracking the progress of loading an individual resource. Note that this method is invoked once per load where as the
web method may be invoked multiple times.