Clojure - Map two hash-maps based on key value

Question

I have a two sets of maps similar to

[{:id 101 :price 40.00} {:id 102 :price 50.00} {:id 103 :price 30.00}]

[{:id 101 :price 45.00} {:id 102 :price 50.00} {:id 103 :price 20.00}]

I am trying to match each map in the first sequence with counterpart in the second based on the "id" key so that I can determine a new price.

The logic for getting the new price seems straightforward enough, but I can't seem to get the two maps to line up. I assumed the map function would be what I need but after spending some time in the REPL, I wasn't able to produce the desired result.

Could someone please point me in the right direction?

A. Webb · Accepted Answer · 2013-08-23 15:22:48Z

2

(def data1 [{:id 101 :price 40.00} {:id 102 :price 50.00} {:id 103 :price 30.00}])
(def data2 [{:id 101 :price 45.00} {:id 102 :price 50.00} {:id 103 :price 20.00}])

(require '[clojure.set :as set])

(set/join data1 (map #(set/rename-keys % {:price :new-price}) data2))

;=> #{{:new-price 45.0, :price 40.0, :id 101}
;     {:new-price 20.0, :price 30.0, :id 103}
;     {:new-price 50.0, :price 50.0, :id 102}}

edited Aug 23, 2013 at 15:22

answered Aug 23, 2013 at 14:47

A. Webb

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