rhai/doc/src/language/oop.md

Object-Oriented Programming (OOP)

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Rhai does not have objects per se, but it is possible to simulate object-oriented programming.

Use [Object Maps] to Simulate OOP

Rhai's [object maps] has special support for OOP.

Rhai concept	Maps to OOP
[Object maps]	objects
[Object map] properties holding values	properties
[Object map] properties that hold [function pointers]	methods

When a property of an [object map] is called like a method function, and if it happens to hold a valid [function pointer] (perhaps defined via an [anonymous function]), then the call will be dispatched to the actual function with this binding to the [object map] itself.

Use Anonymous Functions to Define Methods

[Anonymous functions] defined as values for [object map] properties take on a syntactic shape that resembles very closely that of class methods in an OOP language.

Anonymous functions can also capture variables from the defining environment, which is a very common OOP pattern. Capturing is accomplished via a feature called [automatic currying] and can be turned off via the [no_capture] feature.

Examples

// Define the object
let obj =
     #{
          data: 0,
          increment: |x| this.data += x,    // when called, 'this' binds to 'obj'
          update: |x| this.data = x,        // when called, 'this' binds to 'obj'
          action: || print(this.data)       // when called, 'this' binds to 'obj'
     };

// Use the object
obj.increment(1);
obj.action();                               // prints 1

obj.update(42);
obj.action();                               // prints 42