Special Support for OOP via Object Maps

Object maps can be used to simulate object-oriented programming (OOP) by storing data as properties and methods as properties holding function pointers.

If an object map‘s property holds a function pointer, the property can simply be called like a normal method in method-call syntax. This is a short-hand to avoid the more verbose syntax of using the call function keyword.

When a property holding a function pointer or a closure is called like a method, it is replaced as a method call on the object map itself:


#![allow(unused)]
fn main() {
let obj = #{
                data: 40,
                action: || this.data += x    // 'action' holds a closure
           };

obj.action(2);                               // calls the function pointer with `this` bound to 'obj'

obj.call(obj.action, 2);                     // <- the above de-sugars to this

obj.data == 42;

// To achieve the above with normal function pointer call will fail.

fn do_action(map, x) { map.data += x; }      // 'map' is a copy

obj.action = Fn("do_action");

obj.action.call(obj, 2);                     // a copy of 'obj' is passed by value

obj.data == 42;                              // 'obj.data' is not changed
}