rhaj/rhai_engine/rhaibook/language/object-maps-oop.md

Special Support for OOP via Object Maps

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See the pattern on [_Simulating Object-Oriented Programming_][OOP] for more details.

[Object maps] can be used to simulate [object-oriented programming (OOP)][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.

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 = do_action;                      // <- de-sugars to 'Fn("do_action")'

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

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