rust / intermediate
Snippet
Trait Objects and Dynamic Dispatch
Trait objects enable dynamic dispatch, allowing you to work with values of different types through a common interface. The `dyn Trait` syntax creates a runtime-polymorphic reference. This comes with a small performance cost (vtable lookup) but provides flexibility that static dispatch cannot achieve.
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trait Drawable {fn draw(&self);fn area(&self) -> f64;}struct Circle {radius: f64,}struct Rectangle {width: f64,height: f64,}impl Drawable for Circle {fn draw(&self) {println!("Drawing a circle with radius {}", self.radius);}fn area(&self) -> f64 {std::f64::consts::PI * self.radius * self.radius}}impl Drawable for Rectangle {fn draw(&self) {println!("Drawing a rectangle {}x{}", self.width, self.height);}fn area(&self) -> f64 {self.width * self.height}}fn render_all(drawables: Vec<&dyn Drawable>) {for d in drawables {d.draw();}}fn main() {let shapes: Vec<&dyn Drawable> = vec![&Circle { radius: 2.0 },&Rectangle { width: 3.0, height: 4.0 },];render_all(shapes);let total_area: f64 = shapes.iter().map(|s| s.area()).sum();println!("Total area: {}", total_area);}
Breakdown
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Vec<&dyn Drawable>
A vector of trait objects - each holds a reference to any type implementing Drawable
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fn draw(&self)
Method signature in trait - &self enables dynamic dispatch
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dyn Drawable
Dynamic dispatch marker - Rust uses a vtable at runtime to resolve method calls