I'm having a problem stringing some forms together to do some ETL on a result set from a korma function.
I get back from korma sql:
({:id 1 :some_field "asd" :children [{:a 1 :b 2 :c 3} {:a 1 :b 3 :c 4} {:a 2 :b 2 :c 3}] :another_field "qwe"})
I'm looking to filter this result set by getting the "children" where the :a keyword is 1.
My attempt:
;mock of korma result
(def data '({:id 1 :some_field "asd" :children [{:a 1 :b 2 :c 3} {:a 1 :b 3 :c 4} {:a 2 :b 2 :c 3}] :another_field "qwe"}))
(-> data
first
:children
(filter #(= (% :a) 1)))
What I'm expecting here is a vector of hashmaps that :a is set to 1, i.e :
[{:a 1 :b 2 :c 3} {:a 1 :b 3 :c 4}]
However, I'm getting the following error:
IllegalArgumentException Don't know how to create ISeq from: xxx.core$eval3145$fn__3146 clojure.lang.RT.seqFrom (RT.java:505)
From the error I gather it's trying to create a sequence from a function...though just not able to connect the dots as to why.
Further, if I separate the filter function entirely by doing the following:
(let [children (-> data first :children)]
(filter #(= (% :a) 1) children))
it works. I'm not sure why the first-thread is not applying the filter function, passing in the :children vector as the coll argument.
Any and all help much appreciated.
Thanks
You want the thread-last macro:
(->> data first :children (filter #(= (% :a) 1)))
yields
({:a 1, :b 2, :c 3} {:a 1, :b 3, :c 4})
The thread-first macro in your original code is equivalent to writing:
(filter (:children (first data)) #(= (% :a) 1))
Which results in an error, because your anonymous function is not a sequence.