2024 Rust现代实用教程Generic泛型

一、Generic structures泛型结构体

泛型是一种编程语言的特性，它允许在代码中使用参数化类型，以便在不同地方使用
相同的代码逻辑处理多种数据类型，而无需为每种类型编写单独的代码！

作用：
1．提高代码的重用性
2．提高代码的可读性
3．提高代码的抽象度

1.泛型的应用类型

1．泛型定义结构体\枚举
2．泛型定义函数
3．泛型与特质

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

#[derive(Debug)]
struct PointTwo<T, E> {
    x: T,
    y: E,
}
fn main() {
    let c1 = Point { x: 1.0, y: 2.0 };
    let c2 = Point { x: 'x', y: 'y' };
    println!("c1 {:?} c2 {:?}", c1, c2);

    let c = PointTwo { x: 1.0, y: 'z' };
    println!("{:?}", c);
    // Zero-Cost Abstraction
}

编译及运行：

 cargo run
   Compiling ch1_generic_struct v0.1.0 (/home/wangji/installer/rust/project/ch23_generic_struct)
warning: fields `x` and `y` are never read
 --> src/main.rs:3:5
  |
2 | struct Point<T> {
  |        ----- fields in this struct
3 |     x: T,
  |     ^
4 |     y: T,
  |     ^
  |
  = note: `Point` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis
  = note: `#[warn(dead_code)]` on by default

warning: fields `x` and `y` are never read
  --> src/main.rs:9:5
   |
8  | struct PointTwo<T, E> {
   |        -------- fields in this struct
9  |     x: T,
   |     ^
10 |     y: E,
   |     ^
   |
   = note: `PointTwo` has a derived impl for the trait `Debug`, but this is intentionally ignored during dead code analysis

warning: `ch1_generic_struct` (bin "ch1_generic_struct") generated 2 warnings
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.30s
     Running `target/debug/ch1_generic_struct`
c1 Point { x: 1.0, y: 2.0 } c2 Point { x: 'x', y: 'y' }
PointTwo { x: 1.0, y: 'z' }

二、Generic Function泛型函数

在Rust中，泛型也可以用于函数，使得函数能够处理多种类型的参数，提高代码的重用性和灵活性

1．泛型与普通函数
2．泛型与结构体中的方法

// 交换
fn swap<T>(a: T, b: T) -> (T, T) {
    (b, a)
}

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

impl<T> Point<T> {
    // 构造函数
    fn new(x: T, y: T) -> Self {
        Point { x, y }
    }
    // 方法
    fn get_coordinates(&self) -> (&T, &T) {
        (&self.x, &self.y)
    }
}

fn main() {
    let result = swap::<f64>(0.1, 1.0);
    let result: (f64, f64) = swap(0.1, 1.0);
    println!("{:?}", result);

    let str2 = swap("hh", "tt");
    println!("str2.0 {} str2.1 {}", str2.0, str2.1);

    let str2 = swap(str2.0, str2.1);
    println!("str2.0 {} str2.1 {}", str2.0, str2.1);

    let i32_point = Point::new(2, 3);
    let f64_point = Point::new(2.0, 3.0);
    let (x1, y1) = i32_point.get_coordinates();
    let (x2, y2) = f64_point.get_coordinates();
    println!("i32 point: x= {} y= {}", x1, y1);
    println!("f64 point: x= {} y= {}", x2, y2);

    // String 不要用&str
    //最好使用：let string_point = Point::new("xxx".to_owned(), "yyyy".to_owned());
    let string_point = Point::new("xxx", "yyyy");
    println!("string point x = {} y = {}", string_point.x, string_point.y);
}

编译及运行

 cargo run
   Compiling ch24_func v0.1.0 (/home/wangji/installer/rust/project/ch24_func)
warning: unused variable: `result`
  --> src/main.rs:23:9
   |
23 |     let result = swap::<f64>(0.1, 1.0);
   |         ^^^^^^ help: if this is intentional, prefix it with an underscore: `_result`
   |
   = note: `#[warn(unused_variables)]` on by default

warning: `ch24_func` (bin "ch24_func") generated 1 warning
    Finished `dev` profile [unoptimized + debuginfo] target(s) in 0.33s
     Running `target/debug/ch24_func`
(1.0, 0.1)
str2.0 tt str2.1 hh
str2.0 hh str2.1 tt
i32 point: x= 2 y= 3
f64 point: x= 2 y= 3
string point x = xxx y = yyyy

参考

• 2024 Rust现代实用教程