objects.ktg

; `object` declares a named template.  `make` stamps a
; mutable instance (context!) from the template.  Methods
; access the instance through `self`.

; --- Minimal shape ---
Counter: object [
  field/optional [n [integer!] 0]

  increment: does [self/n: self/n + 1]
  value:     does [self/n]
]

c: make Counter []
c/increment
c/increment
print c/value                      ; 2

; --- Required + optional fields ---
Person: object [
  field/required [name [string!]]
  field/required [age  [integer!]]
  field/optional [tag  [string!] "friend"]

  greet: does [
    rejoin ["Hi, I'm " self/name " (" self/tag ")"]
  ]
]

p: make Person [name: "Kai" age: 30]
print p/greet                      ; Hi, I'm Kai (friend)

; --- Clone an instance ---
; `make` on an instance copies fields, applies overrides.
p2: make p [age: 25  tag: "rival"]
print p2/name                      ; Kai
print p2/age                       ; 25
print p2/tag                       ; rival
print p/age                        ; 30

; --- Methods with params ---
Account: object [
  field/required [owner   [string!]]
  field/optional [balance [money!]  $0.00]

  deposit: function [amount [money!]] [
    self/balance: self/balance + amount
  ]
  summary: does [
    rejoin [self/owner ": " self/balance]
  ]
]

a: make Account [owner: "Kai"]
a/deposit $50.00
a/deposit $12.34
print a/summary                    ; Kai: $62.34

; --- Templates are not mutable; instances are ---
; Mutating Counter directly would raise 'mutation'.
; Mutating `c` works -- instances are plain contexts.