Is there a straight-forward way to select a submap containing a transformed submap of each map-value in a nested map using specter?
An example: cr is a nested map,
{:marks {:these :values :are :omitted},
:scores {:to :simplify :the :example},
:results {1 {:total 8, :sums {:p1 5, :p2a 3}, :check true},
2 {:total 8, :sums {:p1 9, :p2b -1}, :check false}}}
and from this I want to extract a map (int -> boolean) containing
for each key in :results, the value associated with the :check key,
in this case {1 true 2 false}
I can do it in two steps as
(:results (spc/transform [:results spc/MAP-VALS] :check cr))
or, in the general case where the desired submap is not at the top level
(spc/select-one [...... :results] (spc/transform .... cr))
Without specter, the transformation can be expressed quite similarly as (and arguably no less clearly) as
(mapmap #(:check %2) (:results cr))
where mapmap is
(defn mapmap
"creates a map, by mapping f over the values in m
f is a function with two arguments, and is passed
the key and the value "
[f m]
(reduce-kv #(assoc %1 %2 (f %2 %3) ) {} m)
)
I feel like I am is missing something, as I cannot express it in specter as a single navigation.
Can this query be expressed in a single select or transform using specter?
Recursive map query using specter seems related, but I don't quite get how recursive paths work or how to use them for the transform.
The missing piece was the transformed navigator:
(transformed path update-fn)
Navigates to a view of the current value by transforming it with the
specified path and update-fn.
Which can be used in the desired one-liner
(spc/select-one [:results (spc/transformed [spc/MAP-VALS] :check)] cr)
==> {1 true, 2 false}