I've a vector of maps like this:
[{:categoryid 1, :categoryname "foo" } {:categoryid 2, :categoryname "bar" } {:categoryid 3, :categoryname "baz" }] and would like to generate a map of maps like this for searching by categoryname
{"foo" {:categoryid 1, :categoryname "foo" }, "bar" {:categoryid 2, :categoryname "bar" }, "baz" {:categoryid 3, :categoryname "baz" }} How can I do this?
Another way: (into {} (map (juxt :categoryname identity) [...]))
(reduce (fn [m {catname :categoryname :as input}] (assoc m catname input)) {} [{:categoryid 1, :categoryname "foo" } {:categoryid 2, :categoryname "bar" } {:categoryid 3, :categoryname "baz" }]) Better yet,
(#(zipmap (map :categoryname %) %) [{:categoryid 1, :categoryname "foo" } {:categoryid 2, :categoryname "bar" } {:categoryid 3, :categoryname "baz" }]) 
(ns code.groupby (:use clojure.contrib.seq-utils)) (def vector-of-maps [ {:categoryid 1, :categoryname "foo" } {:categoryid 2, :categoryname "bar" } {:categoryid 3, :categoryname "baz" } ]) (group-by :categoryname vector-of-maps) Gives you a map of Vectors of maps
{"bar" [{:categoryid 2, :categoryname "bar"}], "baz" [{:categoryid 3, :categoryname "baz"}], "foo" [{:categoryid 1, :categoryname "foo"}]} (which I now realise isn't what you wanted...sorry)
I haven't tested it in Clojure, but in ClojureScript this variant appears to be faster than others:
(reduce #(assoc %1 (:categoryname %2) %2) {} [...]) 