Trait exercises - rust-course

50.13.1Shapes drawing¶

We define first the Shape trait:

trait Shape {
  fn draw(&self);
}

Then the rectangle:

struct Rectangle {
  x: i32,
  y: i32,
  width: u32,
  height: u32,
}

Its implementation:

impl Shape for Rectangle {
  fn draw(&self) {
    println!("Drawing rectangle {}x{} at ({}, {}).",
             self.width, self.height, self.x, self.y);
  }
}

The Circle structure:

struct Circle {
  x: i32,
  y: i32,
  radius: u32,
}

Its implementation:

impl Shape for Circle {
  fn draw(&self) {
    println!("Drawing circle of radius {} at ({}, {}).",
             self.radius, self.x, self.y);
  }
}

The Drawing contains now a shapes field that is a vector of shapes:

struct Drawing<'a> {
  shapes: Vec<&'a (dyn Shape + 'a)>,
}

In the implementation of the Drawing structure, we now have a draw() method that iterates over all shapes to call their draw() methods, and a add_shape() method to add new shapes:

impl<'a> Drawing<'a> {

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

  fn add_shape(&mut self, shape: &'a dyn Shape) {
    self.shapes.push(shape);
  }
}

Let us instantiate a rectangle and a circle:

let rect = Rectangle { x: 4, y: 6, width: 20, height: 30 };
let circ = Circle { x: 5, y: 2, radius: 10 };

We then create the Drawing object and add our shapes to it, and finally trigger the drawing:

{
  let mut drawing = Drawing { shapes: Vec::new() };
  drawing.add_shape(&rect);
  drawing.add_shape(&circ);
  drawing.draw();
}

Drawing rectangle 20x30 at (4, 6).

Drawing circle of radius 10 at (5, 2).

()

50.13 Trait exercises

50.13.1Shapes drawing¶