rust - trait学习

通过对《Rust 程序设计语言》，《通过例子学 Rust 中文版》以及令狐一冲老师对相关知识点的学习总结而成。

1 trait 的基本含义

• 1，trait 用于定义与其他类型共享的功能，类似于其他语言中的接口
  • （1），可以通过trait以抽象的方式定义共享的行为
  • （2），可以使用trait bounds指定泛型是任何拥有特定行为的类型

2 定义trait

pub trait GetInformation {
    fn get_name(&self) -> &String;
    fn get_age(&self) -> u32;
}

3 实现trait

pub trait GetInformation {
    fn get_name(&self) -> &String;

    fn get_age(&self) -> u32;
}

pub struct Student {
    pub name: String,
    pub age: u32,
}

impl GetInformation for Student {
    fn get_name(&self) -> &String {
        &self.name
    }

    fn get_age(&self) -> u32 {
        self.age
    }
}

pub struct Teacher {
    pub name: String,
    pub age: u32,
    pub subject: String,
}

impl GetInformation for Teacher {
    fn get_name(&self) -> &String {
        &self.name
    }

    fn get_age(&self) -> u32 {
        self.age
    }
}

fn main() {

    let s = Student {name: "xiaoming".to_string(), age: 15};
    let t = Teacher {name: String::from("xiaohuang"), age: 35, subject: String::from("math")};

    println!("Student, name = {}, age = {}", s.get_name(), s.get_age());
    println!("Teacher, name = {}, age = {}", t.get_name(), t.get_age());

    println!("Hello, world!");
}

运行结果：

rlk@rlk:lear_trait$ cargo run
   Compiling lear_trait v0.1.0 (/home/rlk/work/learn_rust/lear_trait)
    Finished dev [unoptimized   debuginfo] target(s) in 0.70s
     Running `target/debug/lear_trait`
Student, name = xiaoming, age = 15
Teacher, name = xiaohuang, age = 35
Hello, world!
rlk@rlk:lear_trait$

4 trait作为参数

pub trait GetInformation {
    fn get_name(&self) -> &String;

    fn get_age(&self) -> u32;
}

pub struct Student {
    pub name: String,
    pub age: u32,
}

impl GetInformation for Student {
    fn get_name(&self) -> &String {
        &self.name
    }

    fn get_age(&self) -> u32 {
        self.age
    }
}

pub struct Teacher {
    pub name: String,
    pub age: u32,
    pub subject: String,
}

impl GetInformation for Teacher {
    fn get_name(&self) -> &String {
        &self.name
    }

    fn get_age(&self) -> u32 {
        self.age
    }
}

fn print_information(item: impl GetInformation) {
    println!("name = {}", item.get_name());
    println!("age = {}", item.get_age());
}

fn main() {

    let s = Student {name: "xiaoming".to_string(), age: 15};
    let t = Teacher {name: String::from("xiaohuang"), age: 35, subject: String::from("math")};

    //println!("Student, name = {}, age = {}", s.get_name(), s.get_age());
    //println!("Teacher, name = {}, age = {}", t.get_name(), t.get_age());
    print_information(s);
    print_information(t);

    println!("Hello, world!");
}

运行结果：

rlk@rlk:lear_trait$ cargo run
    Finished dev [unoptimized   debuginfo] target(s) in 0.00s
     Running `target/debug/lear_trait`
name = xiaoming
age = 15
name = xiaohuang
age = 35
Hello, world!
rlk@rlk:lear_trait$

5 默认实现

trait SchoolName {
    fn get_school_name(&self) -> String {
        String::from("HongXingSchool")
    }
}

pub struct Student {
    pub name: String,
    pub age: u32,
}

impl SchoolName for Student {}

pub struct Teacher {
    pub name: String,
    pub age: u32,
    pub subject: String,
}

impl SchoolName for Teacher {
    fn get_school_name(&self) -> String {
        String::from("GuangMingSchool")
    }
}

完整的测试程序

pub trait GetInformation {
    fn get_name(&self) -> &String;

    fn get_age(&self) -> u32;
}

trait SchoolName {
    fn get_school_name(&self) -> String {
        String::from("HongXingSchool")
    }
}

pub struct Student {
    pub name: String,
    pub age: u32,
}

impl SchoolName for Student {}

impl GetInformation for Student {
    fn get_name(&self) -> &String {
        &self.name
    }

    fn get_age(&self) -> u32 {
        self.age
    }
}

pub struct Teacher {
    pub name: String,
    pub age: u32,
    pub subject: String,
}

impl SchoolName for Teacher {
    fn get_school_name(&self) -> String {
        String::from("GuangMingSchool")
    }
}

impl GetInformation for Teacher {
    fn get_name(&self) -> &String {
        &self.name
    }

    fn get_age(&self) -> u32 {
        self.age
    }
}

fn print_information(item: impl GetInformation) {
    println!("name = {}", item.get_name());
    println!("age = {}", item.get_age());
}

fn main() {
    let s = Student {name: "xiaoming".to_string(), age: 15};
    let t = Teacher {name: String::from("xiaohuang"), age: 35, subject: String::from("math")};

    //println!("Student, name = {}, age = {}", s.get_name(), s.get_age());
    //println!("Teacher, name = {}, age = {}", t.get_name(), t.get_age());
    let s_school_name = s.get_school_name();
    println!("Student school name = {}", s_school_name);

    let t_school_name = t.get_school_name();
    println!("Teacher school name = {}", t_school_name);

    print_information(s);
    print_information(t);

    println!("Hello, world!");
}

运行结果

rlk@rlk:lear_trait$ cargo run
   Compiling lear_trait v0.1.0 (/home/rlk/work/learn_rust/lear_trait)
    Finished dev [unoptimized   debuginfo] target(s) in 0.32s
     Running `target/debug/lear_trait`
Student school name = HongXingSchool
Teacher school name = GuangMingSchool
name = xiaoming
age = 15
name = xiaohuang
age = 35
Hello, world!
rlk@rlk:lear_trait$

6 trait_bound

6.1 trait_bound语法

//trait直接作为参数的写法
fn print_information(item: impl GetInformation) {}
//使用trait bound的写法一
fn print_information<T: GetInformation>(item: T) {}
//使用trait bound的写法一
fn print_information<T>(item: T)
	where T: GetInformation
{}

6.2 trait_bound语法

//trait直接作为参数的写法
//fn print_information(item: impl GetInformation) {
//使用trait bound的写法
//fn print_information<T: GetInformation>(item: T) {

trait GetName {
    fn get_name(&self) -> &String;
}

trait GetAge {
    fn get_age(&self) -> u32;
}

fn print_information<T: GetName   GetAge>(item: T) {
    println!("name = {}", item.get_name());
    println!("age = {}", item.get_age());
}
/*
fn print_information<T>(item: T)
	where T: GetName   GetAge
{
    println!("name = {}", item.get_name());
    println!("age = {}", item.get_age());
}
*/

fn print_information<T>(item: T)
	where T: GetName   GetAge
{
    println!("name = {}", item.get_name());
    println!("age = {}", item.get_age());
}

pub struct Student {
    pub name: String,
    pub age: u32,
}

impl GetName for Student {
    fn get_name(&self) -> &String {
        &self.name
    }
}

impl GetAge for Student {
    fn get_age(&self) -> u32 {
        self.age
    }
}

fn main() {
    let s = Student {name: "xiaoming".to_string(), age: 15};

    print_information(s);

    println!("Hello, world!");
}

运行结果：

rlk@rlk:learn_trait2$ cargo run
    Finished dev [unoptimized   debuginfo] target(s) in 0.00s
     Running `target/debug/learn_trait2`
name = xiaoming
age = 15
Hello, world!
rlk@rlk:learn_trait2$

7 trait作为返回值

trait GetAge {
    fn get_age(&self) -> u32;
}

#[derive(Debug)]
pub struct Student {
    pub name: String,
    pub age: u32,
}

impl GetAge for Student {
    fn get_age(&self) -> u32 {
        self.age
    }
}

fn produce_item_with_age() -> impl GetAge {
    Student {
        name: String::from("xiaoming"),
        age: 15,
    }
}

fn main() {
    let s = produce_item_with_age();

    println!("student age = {}", s.get_age());

    println!("Hello, world!");
}

运行结果：

rlk@rlk:learn_trait$ cargo run
   Compiling learn_trait v0.1.0 (/home/rlk/projects/learn_trait)
    Finished dev [unoptimized   debuginfo] target(s) in 0.39s
     Running `target/debug/learn_trait`
student age = 15
Hello, world!
rlk@rlk:learn_trait$

8 使用trait bound有条件的实现

pub trait GetName {
    fn get_name(&self) -> &String;
}

pub trait GetAge {
    fn get_age(&self) -> u32;
}

struct PeopleMatchInformation<T, U> {
    master: T,
    student: U,
}

impl<T: GetName   GetAge, U: GetName   GetAge> PeopleMatchInformation<T, U> {
    fn print_all_information(&self) {
        println!("master name = {}", self.master.get_name());
        println!("master age = {}", self.master.get_age());

        println!("student name = {}", self.student.get_name());
        println!("student age = {}", self.student.get_age());
    }
}

struct Teacher {
    name: String,
    age: u32,
}

impl GetName for Teacher {
    fn get_name(&self) -> &String {
        &(self.name)
    }
}


impl GetAge for Teacher {
    fn get_age(&self) -> u32 {
        self.age
    }
}

struct Student {
    name: String,
    age: u32,
}

impl GetName for Student {
    fn get_name(&self) -> &String {
        &(self.name)
    }
}


impl GetAge for Student {
    fn get_age(&self) -> u32 {
        self.age
    }
}

fn main() {
    let s = Student {name: String::from("xiaoming"), age: 15};
    let t = Teacher {name: String::from("xiaohuang"), age: 35};

    let m = PeopleMatchInformation{master: t, student: s};
    m.print_all_information();

    println!("Hello, world!");
}

运行结果：

rlk@rlk:learn_trait2$ cargo run
   Compiling learn_trait2 v0.1.0 (/home/rlk/projects/learn_trait2)
    Finished dev [unoptimized   debuginfo] target(s) in 0.19s
     Running `target/debug/learn_trait2`
master name = xiaohuang
master age = 35
student name = xiaoming
student age = 15
Hello, world!
rlk@rlk:learn_trait2$

这篇好文章是转载于：学新通技术网