62 lines
2.1 KiB
Markdown
62 lines
2.1 KiB
Markdown
Object-Oriented Programming (OOP)
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================================
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{{#include ../links.md}}
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Rhai does not have _objects_ per se, but it is possible to _simulate_ object-oriented programming.
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Use Object Maps to Simulate OOP
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------------------------------
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Rhai's [object maps] has [special support for OOP]({{rootUrl}}/language/object-maps-oop.md).
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| Rhai concept | Maps to OOP |
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| ----------------------------------------------------- | :---------: |
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| [Object maps] | objects |
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| [Object map] properties holding values | properties |
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| [Object map] properties that hold [function pointers] | methods |
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When a property of an [object map] is called like a method function, and if it happens to hold
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a valid [function pointer] (perhaps defined via an [anonymous function] or more commonly as a [closure]),
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then the call will be dispatched to the actual function with `this` binding to the [object map] itself.
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Use Closures to Define Methods
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-----------------------------
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[Anonymous functions] or [closures] defined as values for [object map] properties take on
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a syntactic shape that resembles very closely that of class methods in an OOP language.
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Closures also _[capture][automatic currying]_ variables from the defining environment, which is a very
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common OOP pattern. Capturing is accomplished via a feature called _[automatic currying]_ and
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can be turned off via the [`no_closure`] feature.
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Examples
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--------
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```rust
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let factor = 1;
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// Define the object
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let obj = #{
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data: 0, // object field
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increment: |x| this.data += x, // 'this' binds to 'obj'
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update: |x| this.data = x * factor, // 'this' binds to 'obj', 'factor' is captured
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action: || print(this.data) // 'this' binds to 'obj'
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};
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// Use the object
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obj.increment(1);
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obj.action(); // prints 1
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obj.update(42);
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obj.action(); // prints 42
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factor = 2;
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obj.update(42);
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obj.action(); // prints 84
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```
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