Attachments are used by both iCalendar and vCard. They are either a URI or inline data, and their decoded value will be either a Uri or a Inline, as appropriate.

Besides the methods specific to their class, both kinds of object implement a set of common methods, allowing them to be treated uniformly:

• Uri#to_io, Inline#to_io: return an IO from which the value can be read.
• Uri#to_s, Inline#to_s: return the value as a String.
• Uri#format, Inline#format: the format of the value. This is supposed to be an "iana defined" identifier (like "image/jpeg"), but could be almost anything (or nothing) in practice. Since the parameter is optional, it may be "".

The objects can also be distinguished by their class, if necessary.