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zadikian • today at 2:41 AM • 1 reply • view on HN

It doesn't seem uncommon for someone to generally like Rust but still want to use something OO for UI. I'm in that boat. Never liked OOP much, but it makes sense sometimes.

Replies

antonvs • today at 7:05 AM

What OO features are you thinking of that Rust doesn't have?

Traits give you the ability to model typical GUI OO hierarchies, e.g.:

    trait Widget {
        fn layout(&mut self, constraints: Constraints);
        fn paint(&self, ctx: &mut PaintCtx);
        fn handle_event(&mut self, event: Event);
    }

    struct Button { ... }
    struct Label { ... }

    impl Widget for Button { ... }
    impl Widget for Label { ... }

    let mut widgets: Vec<Box<dyn Widget>> = Vec::new();
Implementation inheritance can be achieved with good old shared functions that take trait arguments, like this:

    fn paint_if_visible<W>(widget: &W, ctx: &mut PaintCtx)
    where
        W: HasBounds + HasVisibility,
    {
        if widget.is_visible() {
            ctx.paint_rect(widget.bounds());
        }
    }
You can also define default methods at the trait level.

This all ends up being much more precise, clear, and strongly typed than the typical OO inheritance model, while still following a similar overall structure.

You can see real world examples of this kind of thing in the various GUI toolkits for Rust, like Iced, gpui, egui, Dioxus, etc.