This is a helpful hint, and probably one that others are already
using, but seemed good to share.
If you're sorting a list of maps on one field, you can use
(sort-by :community list-of-residents)
But sorting on two (or more) fields seems to require a little more
coding:
(sort-by :community (sort-by :last-name list-of-residents))
or
(sort-by #(vector (:community %) (:last-name %)) list-of-
residents)
But the latter version is equivalent to the terser
(sort-by (juxt :community :last-name) list-of-residents)
The juxt function takes functions as an argument (and this includes
function equivalents like keywords) and returns a function that
generates a vector by applying each function in order. (Not clear
enough? Well, from the docstring for juxt:
Takes a set of functions and returns a fn that is the
juxtaposition of those
fns. The returned fn takes a variable number of args, and returns
a vector
containing the result of applying each fn to the args (left-to-
right).
Anyway, the resulting code for sort-by is terse and clear (even if the
reader is not sure about juxt, the prominent key-fields may give the
correct idea).
Thanks for your patience,
ron
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