如何在向量中存储实现相同特征的不同类型并在其上调用常用函数？

Question

我正在学习Rust,我在实现多态方面遇到了困难.我想用数组来存储Circle或者Test.

trait Poli {
    fn area(&self) -> f64;
}

struct Circle {
    x:      f64,
    y:      f64,
    radius: f64,
}

impl Circle {
    fn new (xx: f64, yy: f64, r: f64) -> Circle{
        Circle{ x: xx, y: yy, radius: r }
    }
}

impl Poli for Circle {
   fn area(&self) -> f64 {
       std::f64::consts::PI * (self.radius * self.radius)
   }
}

struct Test {
    x:      f64,
    y:      f64,
    radius: f64,
    test:   f64,
}

impl Test {
    fn new (xx: f64, yy: f64, r: f64, t: f64) -> Circle{
        Test{ x: xx, y: yy, radius: r, test: t, }
    }
}

impl Poli for Test {
    fn area(&self) -> f64 {
        std::f64::consts::PI * (self.radius * self.radius)
    }
}

我不知道如何使用相同的存储类型的向量trait:

let cir  = Circle::new(10f64, 10f64, 10f64);
let test = Test::new(10f64, 10f64, 10f64, 10f64);

//let mut vec: Vec<Poli> = Vec::new();   <---

我想迭代向量并从特征中调用函​​数.有没有办法做到这一点,或者一些替代方案？

我读了特征对象文档,但我认为这不是我想要的.

Answer 1

正如您链接到的页面中所提到的,您需要将Poli实现结构存储为Vec<&Poli>或Vec<Box<Poli>>依赖于您是否要拥有值或仅存储引用:

// Owned
let circle = Circle::new(10f64, 10f64, 10f64);
let test = Test::new(10f64, 10f64, 10f64, 10f64);

let polis = vec![Box::new(circle) as Box<Poli>, Box::new(test) as Box<Poli>];

for poli in polis {
    println!("{}", poli.area());
}

// Reference
let circle = Circle::new(10f64, 10f64, 10f64);
let test = Test::new(10f64, 10f64, 10f64, 10f64);

let polis = vec![&circle as &Poli, &test as &Poli];

for poli in polis {
    println!("{}", poli.area());
}

产量

314.1592653589793
314.1592653589793
314.1592653589793
314.1592653589793

演示