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Question

我有以下数据:

({:seriesId "series 0", :episodeId "0"}
 {:seriesId "series 1", :episodeId "1"}
 {:seriesId "series 1", :episodeId "2"}
 {:seriesId "series 2", :episodeId "3"}
 {:seriesId "series 2", :episodeId "4"}
 {:seriesId "series 2", :episodeId "5"})

并希望将每集与其系列相关联,如下所示:

[{:put-request
  {:item {:seriesId "series 0", :episodeCount 1, :episodeIds #{"0"}}}}
 {:put-request
  {:item {:seriesId "series 1", :episodeCount 2, :episodeIds #{"1" "2"}}}}
 {:put-request
  {:item {:seriesId "series 2", :episodeCount 3, :episodeIds #{"3" "4" "5"}}}}]

目前我遇到以下问题:

[{:put-request
  {:item {:seriesId "series 0", :episodeCount 1, :episodeIds #{"0"}}}}
 {:put-request
  {:item {:seriesId "series 1", :episodeCount 1, :episodeIds #{"1"}}}}
 {:put-request
  {:item {:seriesId "series 1", :episodeCount 1, :episodeIds #{"2"}}}}
 {:put-request
  {:item {:seriesId "series 2", :episodeCount 1, :episodeIds #{"3"}}}}
 {:put-request
  {:item {:seriesId "series 2", :episodeCount 1, :episodeIds #{"4"}}}}
 {:put-request
  {:item {:seriesId "series 2", :episodeCount 1, :episodeIds #{"5"}}}}]

我正在使用该create-or-update-series功能.我不知道如何找到/获取以前添加的系列(如果添加!)使用seriesId.我尝试了很多东西,但这些都是无穷无尽的曲目.

(ns clojure-sscce.core
  (:gen-class)
  (:require clojure.pprint))

(defn create-or-update-series
  ([episodes]
    (create-or-update-series episodes []))
  ([episodes result]
    (if (zero? (count episodes))
      result
      (create-or-update-series (rest episodes)
        (conj result {
          :put-request {
            :item {
              :seriesId (:seriesId (first episodes))
              :episodeCount 1
              :episodeIds #{(:episodeId (first episodes))}}}})))))

;; Tests
(defn -main [& args]
  (let 
    [series0 (mapv (fn [episode-id] {
      :seriesId "series 0"
      :episodeId (str episode-id)}) (range 0 1))
    series1 (mapv (fn [episode-id] {
      :seriesId "series 1"
      :episodeId (str episode-id)}) (range 1 3))
    series2 (mapv (fn [episode-id] {
      :seriesId "series 2"
      :episodeId (str episode-id)}) (range 3 6))]

    (clojure.pprint/pprint
      (concat series0 series1 series2))

    (clojure.pprint/pprint 
      (create-or-update-series (concat series0 series1 series2)))))

请注意,这{:put-request {:item { ...是必需的,因为新映射应该是PUT到DynamoDB.

会爱你的帮助!

Answer 1

group-by这样的事情非常好.这是与for理解相结合的一次尝试:

(defn group-by-series [episodes]
  (let [grouped (group-by :seriesId episodes)]
    (for [[series eps-in-series] grouped]
      {:seriesId series 
       :episodeCount (count eps-in-series)
       :episodeIds (into #{} (map :episodeId eps-in-series))})))

(group-by-series example-data)
;=> ({:seriesId "series 0", :episodeCount 1, :episodeIds #{"0"}} 
;    {:seriesId "series 1", :episodeCount 2, :episodeIds #{"1" "2"}}
;    {:seriesId "series 2", :episodeCount 3, :episodeIds #{"3" "4" "5"}})

for如果需要,您可以在理解中添加DynamoDB内容,或者创建包装函数并将其映射到它们之间.