I am new to functional programming and have a use case where I have a list of Books, I want to iterate over it, do some mapping and return a new List. My code
(defn map-book [books]
((doseq [x books]
(let [lst (create-response x)]
(println "data -> " (json/encode lst))
(json/encode lst)))))
(defn create-response [book]
(let [updated-book (merge {"book-name" (.getBookName book)
"book-page" (.getBookPageCount book)}]
updated-book))
when I try to run this, I am able to get json decoded response in terminal due to println but not the json list as a response from the function. have been stucked around for some time on this.
What I want is something like :
[{
"book-name": "rick boy",
"book-page": 110
},
{
"book-name": "poor boy",
"book-page": 124
}
]
but am getting something like, when I run my unit test:
#object[book_service.book$map_book 0x7915bca3 [book_service.book$map_book@7915bca3]
thanks for any help!
If you want to return new list (or vector), you should avoid doseq
(which is for side effects- for example, printing, and always returns nil
) and use map
or for
instead.
I guess you want to return JSON string for given data and your json
library is actually Cheshire:
Dependencies: [cheshire "5.11.0"]
Require in ns
: [cheshire.core :as json]
Book class:
public class Book {
String bookName;
Long pageCount;
public Book(String name, Long pages) {
bookName = name;
pageCount = pages;
}
public String getBookName() {
return bookName;
}
public Long getBookPageCount() {
return pageCount;
}
}
Clojure code:
(defn get-book-map [book]
{"book-name" (.getBookName book)
"book-page" (.getBookPageCount book)})
(defn encode-books [books]
(json/encode (map get-book-map books)))
Test:
(encode-books [(Book. "rick boy" 110)
(Book. "poor boy" 124)])
=> "[{\"book-name\":\"rick boy\",\"book-page\":110},{\"book-name\":\"poor boy\",\"book-page\":124}]"
(json/decode *1)
=> ({"book-name" "rick boy", "book-page" 110} {"book-name" "poor boy", "book-page" 124})