Object serialization: Difference between revisions

=={{header|EchoLisp}}==

Our classes will be 'struct' objects, with custom #:tostring procedures, as required. The instances are saved/restored to/from local storage. Serialization is performed by JSONifying the objects. References between instances of struct's are kept in the process.

<lang lisp>

(define (person->string self) (format "%a : person." (person-name self)))

(define (writer->string self) (format "%a: writer of %a."

(person-name self)

(writer-books self)))

(define (father->string self) (format "%a: father of %a."

(person-name self)

(map person-name (father-children self))))

; 'classes' definition, with inheritance.

; a writer is a person, too.

(struct person (name) #:tostring person->string)

(struct writer person (books) #:tostring writer->string)

(struct father person (children) #:tostring father->string)

(define simon (writer "Simon" '(my-life my-wife my-bike)))

(define elvis (person "Elvis"))

(define papa (father "papa" (list simon elvis)))

(local-put-value 'simon simon "objects.dat")

📕 local-db: local-put:unknown store : "objects.dat"

;; forgot to create the 'file'.

(local-make-store "objects.dat") → "objects.dat"

(local-put-value 'simon simon "objects.dat")

(local-put-value 'elvis elvis "objects.dat")

(local-put-value 'papa papa "objects.dat")

;; inspect

simon → Simon: writer of (my-life my-wife my-bike).

papa → papa: father of (Simon Elvis).

elvis → Elvis : person.

</lang>

{{output}}

<lang lisp>

;; reboot (close the browser window)

(local-keys 'objects.dat) → ("elvis" "papa" "simon")

(define simon (local-get-value 'simon "objects.dat"))

(define elvis (local-get-value 'elvis "objects.dat"))

(define papa (local-get-value 'papa "objects.dat"))

; data are restored

simon → Simon: writer of (my-life my-wife my-bike).

papa → papa: father of (Simon Elvis).

;; check if references (pointers) are restored

(set-writer-name! simon "Antoinette") → "Antoinette"

simon→ Antoinette: writer of (my-life my-wife my-bike).

;; inspect

papa → papa: father of (Antoinette Elvis). ; YES 😳 !

</lang>