41 lines
1.7 KiB
Markdown
41 lines
1.7 KiB
Markdown
Special Support for OOP via Object Maps
|
|
======================================
|
|
|
|
{{#include ../links.md}}
|
|
|
|
[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] is called like a method, what happens next depends
|
|
on whether the target function is a native Rust function or a script-defined function.
|
|
|
|
If it is a registered native Rust method function, then it is called directly.
|
|
|
|
If it is a script-defined function, the `this` variable within the function body is bound
|
|
to the [object map] before the function is called. There is no way to simulate this behavior
|
|
via a normal function-call syntax because all scripted function arguments are passed by value.
|
|
|
|
```rust
|
|
fn do_action(x) { this.data += x; } // 'this' binds to the object when called
|
|
|
|
let obj = #{
|
|
data: 40,
|
|
action: Fn("do_action") // 'action' holds a function pointer to 'do_action'
|
|
};
|
|
|
|
obj.action(2); // Calls 'do_action' 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.call(obj, 2); // 'obj' is passed as a copy by value
|
|
```
|