I'm scheduled to implement skipDays, skipHours, and ttl today, so I was surfing on the Internet (to the tune of Scott Bakula's Man of La Mancha - Impossible Dream, Nancy Sinatra's Summer Wine, Paul Anka's Diana, to name but a few) looking for blogs which implemented these settings, so that I can continue “My RSS Reader”'s development, and test them using these blogs.
To my surprise, I'm unable to find sites that placed these settings in their blogs, and after surfing for the better part of an hour, I've decided not to implement support for skipDays, skipHours and ttl.
In 2017, with the release of Delphi 10.2 Tokyo, Embarcadero introduced a specialized implementation of the Observer pattern into the System.Classes unit. While it has been in the wild for 9 years, it remains a "hidden" architecture for many, primarily because it serves as the invisible engine behind LiveBindings. Other than live bindings, you can also use the Observer pattern as a way to update component settings to the Windows registry, an .ini file, or persist it elsewhere.
System.Classes