Clojure sort-by - clojure

Question

I'm trying to understand Clojure more and more, i have the following list:
{merchant-data {order-id 72144305, unit-price-dollars 110.0, merchant-discount-dollars 20.5, my-discount-dollars 10.2, session-type CONTROL}, my-data {order-id 72144305, unit-price-dollars 110.5, merchant-discount-dollars 10.0, my-discount-dollars 20.2, session-type control}}
{merchant-data {order-id 72144777, unit-price-dollars 200.0, merchant-discount-dollars 30.0, my-discount-dollars 0.0, session-type TEST}, my-data {order-id 72144777, unit-price-dollars 200.0, merchant-discount-dollars 0.0, my-discount-dollars 30.0, session-type test}}
{merchant-data {order-id 72145239, unit-price-dollars 50.0, merchant-discount-dollars 14.8, my-discount-dollars 2.0, session-type UNMANAGED}, my-data {order-id 72145239, unit-price-dollars 50.0, merchant-discount-dollars 5.0, my-discount-dollars 15.0, session-type unmanaged}}
I'm trying to sort this list based on specific field for example (unit-price-dollars):
(sort-by :unit-price-dollars sorted-result)
for some reason I'm not getting the sorted list, Please help! if this is not the right way, please suggest the right one!

Answer 1

Firstly it always helps if the data structure you are trying to sort is valid Clojure. Secondly you need to specify the full path to the value you want to sort by.
user> (def prices [{:merchant-data {:order-id 72144305, :unit-price-dollars 110.0, :merchant-discount-dollars 20.5, :my-discount-dollars 10.2, :session-type "CONTROL"}, :my-data {:order-id 72144305, :unit-price-dollars 110.5, :merchant-discount-dollars 10.0, :my-discount-dollars 20.2, :session-type "control"}}
{:merchant-data {:order-id 72144777, :unit-price-dollars 200.0, :merchant-discount-dollars 30.0, :my-discount-dollars 0.0, :session-type "TEST"}, :my-data {:order-id 72144777, :unit-price-dollars 200.0, :merchant-discount-dollars 0.0, :my-discount-dollars 30.0, :session-type "test"}}
{:merchant-data {:order-id 72145239, :unit-price-dollars 50.0, :merchant-discount-dollars 14.8, :my-discount-dollars 2.0, :session-type "UNMANAGED"}, :my-data {:order-id 72145239, :unit-price-dollars 50.0, :merchant-discount-dollars 5.0, :my-discount-dollars 15.0, :session-type "unmanaged"}}])
user> (clojure.pprint/pprint (sort-by #(get-in % [:merchant-data :unit-price-dollars]) prices))
({:my-data
{:my-discount-dollars 15.0,
:unit-price-dollars 50.0,
:session-type "unmanaged",
:order-id 72145239,
:merchant-discount-dollars 5.0},
:merchant-data
{:my-discount-dollars 2.0,
:unit-price-dollars 50.0,
:session-type "UNMANAGED",
:order-id 72145239,
:merchant-discount-dollars 14.8}}
{:my-data
{:my-discount-dollars 20.2,
:unit-price-dollars 110.5,
:session-type "control",
:order-id 72144305,
:merchant-discount-dollars 10.0},
:merchant-data
{:my-discount-dollars 10.2,
:unit-price-dollars 110.0,
:session-type "CONTROL",
:order-id 72144305,
:merchant-discount-dollars 20.5}}
{:my-data
{:my-discount-dollars 30.0,
:unit-price-dollars 200.0,
:session-type "test",
:order-id 72144777,
:merchant-discount-dollars 0.0},
:merchant-data
{:my-discount-dollars 0.0,
:unit-price-dollars 200.0,
:session-type "TEST",
:order-id 72144777,
:merchant-discount-dollars 30.0}})
nil

Answer 2

The question itself throws up issues. For example the maps above do not contain unit-price-dollars but their two submaps do. Do you want to sort by the merchant-data one, the my-data one or some combination of both?
Attempting the simpler case, sorting by one of the values (randomly picked merchant-data), converting all the symbol keys to keywords, and putting the individual maps into a collection gives:
(def test-data
[{:merchant-data {:order-id 72144305, :unit-price-dollars 110.0, :merchant-discount-dollars 20.5, :my-discount-dollars 10.2, :session-type :CONTROL}, :my-data {:order-id 72144305, :unit-price-dollars 110.5, :merchant-discount-dollars 10.0, :my-discount-dollars 20.2, :session-type :control}}
{:merchant-data {:order-id 72144777, :unit-price-dollars 200.0, :merchant-discount-dollars 30.0, :my-discount-dollars 0.0, :session-type :TEST}, :my-data {:order-id 72144777, :unit-price-dollars 200.0, :merchant-discount-dollars 0.0, :my-discount-dollars 30.0, :session-type :test}}
{:merchant-data {:order-id 72145239, :unit-price-dollars 50.0, :merchant-discount-dollars 14.8, :my-discount-dollars 2.0, :session-type :UNMANAGED}, :my-data {:order-id 72145239, :unit-price-dollars 50.0, :merchant-discount-dollars 5.0, :my-discount-dollars 15.0, :session-type :unmanaged}}])
(sort-by (comp :merchant-data :unit-price-dollars) test-data)
; =>
;({:merchant-data {:order-id 72145239, :unit-price-dollars 50.0, :merchant-discount-dollars 14.8, :my-discount-dollars 2.0, :session-type :UNMANAGED}, :my-data {:order-id 72145239, :unit-price-dollars 50.0, :merchant-discount-dollars 5.0, :my-discount-dollars 15.0, :session-type :unmanaged}}
; {:merchant-data {:order-id 72144305, :unit-price-dollars 110.0, :merchant-discount-dollars 20.5, :my-discount-dollars 10.2, :session-type :CONTROL}, :my-data {:order-id 72144305, :unit-price-dollars 110.5, :merchant-discount-dollars 10.0, :my-discount-dollars 20.2, :session-type :control}}
; {:merchant-data {:order-id 72144777, :unit-price-dollars 200.0, :merchant-discount-dollars 30.0, :my-discount-dollars 0.0, :session-type :TEST}, :my-data {:order-id 72144777, :unit-price-dollars 200.0, :merchant-discount-dollars 0.0, :my-discount-dollars 30.0, :session-type :test}})
If this isn't what you are after, then you're going to have to make your question clearer.