I have a type that's an extended date-time. It can be constructed with the
usual year, month, day parameters but (for legacy reasons) the month can be
overloaded to mean extra things. E.g. a month of 21 means 'spring', 33
means 'third quarter'. I want to construct this type in a way that it
preserves that information (so, for example, it can print itself
appropriately), but that has comparison and equality with other dates.
I want to extend clj-time somehow. My first thought is write a type that
construct with the given arguments and implements the
clj-time/DateTimeProtocol, converting whenever required (I don't need high
performance).
(defprotocol IWeirdDate
(as-date [this])
(pp [this]))
(defrecord WeirdDate [year month day]
IWeirdDate
(pp [this] (condp = month
21 (str "Spring " year)
33 (str "Third Quarter of " year)
(str (as-date this))))
(as-date [this]
(let [[y m d] (condp = month
21 [year 3 day]
33 [year 7 1] ; third quarter
; ... others
; default
[year month day])]
(clj-time/date-time y m d)))
clj-time/DateTimeProtocol
(clj-time/year [this] (clj-time/year (as-date this)))
(clj-time/month [this] (clj-time/month (as-date this)))
(clj-time/day [this] (clj-time/day (as-date this)))
; ... and the rest of DateTimeProtocol
)
Is this the right way to do this? Could I somehow make this implicit and
avoid re-writing the DateTimeProtocol implementations?
Cheers
Joe
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