Rust 编程视频教程（进阶）——001 泛型

视频地址

头条地址：https://www.ixigua.com/i6775861706447913485
Ｂ站地址：https://www.bilibili.com/video/av81202308/

讲解内容

1、泛型是具体类型或者其它属性的抽象替代，用于减少代码重复。

2、在函数定义中使用泛型。
例子：
++++++++不使用泛型+++++++++++

//for i32
fn largest_i32(list: &[i32]) -> i32 {
	let mut leargest = list[0];
	for &item in list.iter() {
		if item > largest {
			largest = item;
		}
	}
	largest
}

//for char
fn largest_char(list: &[char]) -> char {
	let mut leargest = list[0];
	for &item in list.iter() {
		if item > largest {
			largest = item;
		}
	}
	largest
}

fn main(){
	let number_list = vec![1, 2, 22, 3, 42];
	let r1 = largest_i32(&number_list);
	println!("r1 = {}", r1);
	let char_list = vec!['a', 'y', 'c', 'd'];
	let r2 = largest_char(&char_list);
	println!("r2 = {}", r2);
}

//+++++++++使用泛型：会报错的函数++++++++++++
fn largest(list: &[T]) -> T { //注意，要实现比较和复制的trait才行，否则报错
	let mut largest = list[0];
	for &item in list.iter() {
		if item > largest {
			largest = item;
		}
	}
	largest
}

fn main(){
	let number_list = vec![1, 2, 22, 3, 42];
	let r1 = largest_i32(&number_list);
	println!("r1 = {}", r1);
	let char_list = vec!['a', 'y', 'c', 'd'];
	let r2 = largest_char(&char_list);
	println!("r2 = {}", r2);
}

3、在结构体中使用泛型。
例子1：

#[derive(Debug)]
struct Point {
	x: T,
	y: T,
}

fn main() {
	let integer = Point {x: 1, y: 2};
	println!("{:#?}", integer);
	let float = Point {x: 0.99, y: 1.99};
	println!("{:#?}", float);
}

例子2：

#[derive(Debug)]
struct Point {
	x: T,
	y: U,
}

fn main() {
	let a = Point {x: 1, y: 2.0};
	println!("{:#?}", a);
	let b = Point {x: 1, y: 1.99};
	println!("{:#?}", b);
}

4、枚举中的泛型

//复习
enum Option {
	Some(T),
	None,
}

enum Result {
	Ok(T),
	Err(e),
}

5、方法中的泛型

struct Point {
	x: T,
	y: T,
}

impl Point {
	fn get_x(&self) -> &T {
		&self.x
	}
	fn get_y(&self) -> &T {
		&self.y
	}
}
fn main() {
	let p = Point {x: 1, y: 2};
	println!("p.x = {}", p.get_x());
	println!("p.y = {}", p.get_y());
}

例子2：方法和结构体中使用不同的类型

struct Point {
	x: T,
	y: U,
}
impl Point {
	fn mixup(self, other: Point) -> Point {
		Point {
			x: self.x,
			y: other.y,
		}
	}
}
fn main() {
	let p1 = Point { x: 5, y: 10.4 };
	let p2 = Point { x: "Hello", y: 'c'};
	let p3 = p1.mixup(p2);
	println!("p3.x = {}, p3.y = {}", p3.x, p3.y);
}

6、使用泛型并不会造成程序性能上的损失。rust通过在编译时进行泛型代码的单态化来保证效率。单态化时通过填充编译时使用的具体类型，将通用代码转换为特定代码的过程。