Construct a RSet from RFC string

[rlanvin]

With the Python version (python dateutils), it is possible to parse a RFC string with multiple RRULE lines (or RDATE, EXDATE, EXRULE) directly into a RSet. That could be interesting to have as well.

This will require some refactoring of RRule::parseRfcString() to make it a factory method, or coding an actual factory method on top of it.

The constructor would still only return a RRule since it is probably not possible and not advisable to have the constructor returns a different object.

A RSet should also be able to be formatted into a RFC String with multiple lines.

If this is a feature that would be useful, leave a 👍

[rlanvin]

Done.

[coffeduong]

Is there any way to refactor RSet back to RFC string?

[rlanvin]

At the moment no. The problem is that, according to the RFC, there can be only one DTSTART property for the entire set. However, a RSet object in this library is more flexible and allow combining multiple RRULE, each with a different DTSTART property. This cannot be expressed in a RFC-compliant way. So I don't know how to handle these cases. I'm open to suggestions.

[coffeduong]

Ok, I'll try. If there is any new idea, I'll ping you back