
use std::any::Any;
//Shape is Prototype
trait Shape {
fn clone(&self) -> Box<dyn Shape>;
fn as_any(&self) -> &dyn Any;
}
//Square is ConcretePrototype
#[derive(Debug)]
struct Square {
line_count: i32
}
impl Shape for Square {
fn clone(&self) -> Box<dyn Shape> {
Box::from(Square {
line_count: self.line_count
})
}
fn as_any(&self) -> &dyn Any { self }
}
//ShapeMaker contains a Shape
struct ShapeMaker {
shape: Box<dyn Shape>
}
//MakeShape creates a copy of the Shape
impl ShapeMaker {
fn make_shape(&self) -> Box<dyn Shape> {
Box::from(self.shape.clone())
}
}
//Client
let square = Square{ line_count: 4 };
let maker = ShapeMaker{
shape: Box::from(square) };
let square1 = maker.make_shape();
let square2 = maker.make_shape();
println!("square1 is {:?}", square1.as_any()
.downcast_ref::<Square>().unwrap());
println!("square2 is {:?}", square2.as_any()
.downcast_ref::<Square>());
| Specify the kinds of objects to create using a prototypical instance, and create new objectsby copying this prototype. |