rust要求每个元素都必须被初始化

struct Point {
    x: u32,
    y: u32,
}
let p: [Point; 2] = [Point { x: 1, y: 2 }, Point { x: 2, y: 3 }];

用不安全的代码 MaybeUninit

use std::{mem::MaybeUninit, ptr};

let p = unsafe {
        let mut p = MaybeUninit::<[Point; 2]>::uninit();
        let h = p.as_mut_ptr() as *mut Point;
        ptr::write(h.offset(0), Point { x: 1, y: 2 });
        ptr::write(h.offset(1), Point { x: 2, y: 3 });

        p.assume_init()
};

用None初始化

let mut p: [Option<Point>; 2] = [None, None];

p[0] = Some(Point { x: 1, y: 2 });
p[1] = Some(Point { x: 2, y: 3 });

用ArrayVec

    let p = {
        let mut p = ArrayVec::<[Point; 2]>::new();

        p.insert(0, Point { x: 1, y: 2 });
        p.insert(1, Point { x: 2, y: 3 });

        p.into_inner()
    };

用Vec来代替数组

let mut test_vec = Vec::with_capacity(20);
for _ in 0..2 {
    vec.push(Point { x: 1, y: 2 });
}

用Clone trait来初始化， 这仅仅对实现了Copy trait 的基本类型有用

#[derive(Debug)]
struct Point {
    a: i32,
    b: u32,
}

impl Copy for Point {}

impl Clone for Point {
    fn clone(&self) -> Point {
        Point{a: self.a, b: self.b}
    }
}

impl Point {
    fn new() -> Point {
        Point {a: 1, b: 2}
    }
}

fn main() {
    let test_var = Point::new();

    let test_array = [Point::new(); 4];
    println!("test_var: {:#?}", test_var);
    println!("test_array: {:#?}", test_array);
}