Useful functions for retrieving items from a list

repl.clj

user=> (def items [{:id 1 :data "hi"} 
                   {:id 2 :data "ho"} 
                   {:id 3 :data "test"}])
#'user/items
user=> (first-where items :id = 1)
{:data "hi", :id 1}
user=> (first-where items :id > 1) ; will return only the first matching item
{:data "ho", :id 2}
user=> (get-where items :id > 1) ; will return all matching items
[{:data "ho", :id 2}
 {:data "test", :id 3}]

vec_of_maps.clj

; Some functions for working with vectors of maps.

(defn first-where
  "Get the first map from a list of maps where the criteria is true.
  The criteria is specified through f, op and key. The element returned
  is the element for which (op (f elem) key) returns truthy."
  [seq f op key]
  (some #(when (op (f %) key) %) seq))

(defn get-where
  "Get all maps from a list of maps where the criteria is true.
  The criteria is specified through f, op and key. The elements returned
  are the elements for which (op (f elem) key) returns truthy."
  [seq f op key]
  (filterv #(op (f %) key) seq))

(defn update-where
  "Update a vector of maps by applying func to each map where criteria is true.
  The criteria is specified through f, op and key. The elements updated are
  the elements for which (op (f elem) key) returns truthy."
  [seq f op key func & args]
  (mapv
    (fn [elem]
        (if (op (f elem) key)
            (apply func elem args)
            elem))
    seq))

(defn transform-where
  "Get and transform all maps from a vector of maps where the criteria is true.
  The criteria is specified through f, op and key. The elements for which
  (op (f elem) key) returns truthy are then passed through xform and returned."
  [seq f op key xform & args]
  (mapv
    #(xform % args)
    (get-where f op key seq)))

vom.cljc

(ns erinite.data.vom
    "Data access and transformation for vector-of-maps data")

(defn criteria-fn
  "Creates a function to test the specified criteria on the supplied input"
  [key op & args]
  (fn [item]
      (apply op (key item) args)))

(defn select
  "Select all maps where the specified criteria is true"
  [vom & criteria]
  (filter
    (apply criteria-fn criteria)
    vom))