[英]How to iterate nested PersistentArrayMap in Clojure/Script
After executing a query against the db, the return of the fuction is the list of maps: 对数据库执行查询后,函数的返回是映射列表:
({:id 1 :name "Book 1" :category "Drama"}
{:id 2 :name "Book 2" :category "Drama"}
{:id 3 :name "Book 3" :category "Poetry"}
{:id 4 :name "Book 4" :category "Poetry"}
{:id 5 :name "Book 5" :category "Fantasy"}
{:id 6 :name "Book 6" :category "Fantasy"}
{:id 7 :name "Book 7" :category "Fantasy"}
{:id 8 :name "Book 8" :category "Science fiction"}
{:id 9 :name "Book 9" :category "Science fiction"}
{:id 10 :name "Book 10" :category "Science fiction"}
...)
So, I group data by category and group-by
function returns a persistent array-map contains strs keys and vector of maps as vals: 因此,我按类别对数据进行分组,并且
group-by
函数返回一个持久的数组映射,其中包含strs键和映射向量作为val:
{"Fantasy" [{:category "Fantasy", :name "Book 5", :id 5}
{:category "Fantasy", :name "Book 6", :id 6}
{:category "Fantasy", :name "Book 7", :id 7}],
"Drama" [{:category "Drama", :name "Book 1", :id 1}
{:category "Drama", :name "Book 2", :id 2}],
"Poetry" [{:category "Poetry", :name "Book 3", :id 3}
{:category "Poetry", :name "Book 4", :id 4}],
"Science fiction" [{:category "Science fiction",
:name "Book 8",
:id 8}
{:category "Science fiction",
:name "Book 9",
:id 9}
{:category "Science fiction",
:name "Book 10",
:id 10}]}
Next, I do this: 接下来,我这样做:
(doseq [[k [{:keys [id name]} v]] data]
(println k)
(println id name))
The side-effect is: 副作用是:
Drama
1 Book1
Poetry
3 Book3
Fantasy
5 Book5
Science fiction
8 Book8
doseq
returned only one value for each key . 每个密钥的
doseq
仅返回一个值 。
How can I get the rest of the values? 我如何获得其余的价值? The result must be:
结果必须是:
Drama
1 Book1
2 Book2
Poetry
3 Book3
4 Book4
Fantasy
5 Book5
6 Book6
7 Book7
Science fiction
8 Book8
9 Book9
10 Book10
you can just make an inner loop like this: 您可以像这样进行内部循环:
(doseq [[k vs] data]
(println k)
(doseq [{:keys [id name]} vs]
(println id name)))
or using single doseq
: 或使用单一
doseq
:
(doseq [[k vs] data
{:keys [id name] :as v} vs]
(when (= v (first vs))
(println k))
(println id name))
also there is one more dirty way to print outer loop string once: 还有一种更脏的方法可以一次打印外循环字符串:
(doseq [[k vs] data
:when (or (println k) true)
{:keys [id name] :as v} vs]
(println id name))
or even like this: 甚至像这样:
(doseq [[k vs] data
{:keys [id name] :as v} (do (println k) vs)]
(println id name))
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