37 lines
1.5 KiB
Markdown
37 lines
1.5 KiB
Markdown
Special Support for OOP via Object Maps
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======================================
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{{#include ../links.md}}
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[Object maps] can be used to simulate [object-oriented programming (OOP)][OOP] by storing data
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as properties and methods as properties holding [function pointers].
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If an [object map]'s property holds a [function pointer], the property can simply be called like
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a normal method in method-call syntax. This is a _short-hand_ to avoid the more verbose syntax
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of using the `call` function keyword.
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When a property holding a [function pointer] is called like a method, what happens next depends
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on whether the target function is a native Rust function or a script-defined function.
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If it is a registered native Rust method function, then it is called directly.
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If it is a script-defined function, the `this` variable within the function body is bound
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to the [object map] before the function is called. There is no way to simulate this behavior
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via a normal function-call syntax because all scripted function arguments are passed by value.
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```rust
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fn do_action(x) { print(this.data + x); } // 'this' binds to the object when called
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let obj = #{
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data: 40,
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action: Fn("do_action") // 'action' holds a function pointer to 'do_action'
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};
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obj.action(2); // Short-hand syntax: prints 42
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// To achieve the above with normal function pointer calls:
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fn do_action(map, x) { print(map.data + x); }
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obj.action.call(obj, 2); // this call cannot mutate 'obj'
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```
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