Inheritance in Rust 1.55

In Rust, inheritance is implemented using trait objects. A trait is a collection of methods that define a certain behavior. A trait object is a reference or a pointer to an instance of a type that implements a certain trait.

To create a trait, use the trait keyword followed by the trait name and its methods. For example:

trait Drawable {
    fn draw(&self);
}

This defines a trait called Drawable that has a single method draw().

To implement this trait for a struct, use the impl keyword followed by the trait name and its implementation. For example:

struct Circle {
    x: f64,
    y: f64,
    radius: f64,
}
impl Drawable for Circle {

    fn draw(&self) {

        // drawing code here...

    }

}

This implements the Drawable trait for the Circle struct, and provides an implementation for the draw() method.

To use inheritance in Rust, we can create a new trait that inherits from another trait using the : ParentTrait syntax. For example:

trait HasArea: Drawable {
    fn area(&self) -> f64;
}

This defines a new trait called HasArea that inherits from Drawable and adds a new method area(). Any type that implements HasArea must also implement Drawable.

To implement this new trait, we can use the impl keyword followed by the trait name and its implementation:

impl HasArea for Circle {
    fn area(&self) -> f64 {
        3.14 * self.radius * self.radius
    }
}

This implements the HasArea trait for the Circle struct, and provides an implementation for the area() method.

Now we can create a vector of Box trait objects and add a Circle object to it:

let mut shapes: Vec> = Vec::new();
let circle = Box::new(Circle {
    x: 0.0,
    y: 0.0,
    radius: 1.0,
});
shapes.push(circle);

We can then loop through the vector and call the draw() method on each object:

for shape in &shapes {
    shape.draw();
}

This will call the draw() method on the Circle object we added earlier.

Similarly, we can call the area() method on objects that implement the HasArea trait:

for shape in &shapes {
    if let Some(has_area) = shape.as_ref().downcast_ref::() {
        println!("Area: {}", has_area.area());
    }
}

This will print the area of the Circle object we added earlier, as it implements the HasArea trait.