Rust的入门篇(下)

这篇博客是rust入门篇下

45. 生命周期注释

// 生命周期


// 下面代码不能通过编译
// longer 函数取 s1 和 s2 两个字符串切片中较长的一个返回其引用值
// 返回值引用可能会返回过期的引用
// fn longer(s1: &str, s2: &str) -> &str {
//     if s2.len() > s1.len() {
//         s2
//     } else {
//         s1
//     }
// }

// 生命周期注释
// &i32        // 常规引用
// &'a i32     // 含有生命周期注释的引用
// &'a mut i32 // 可变型含有生命周期注释的引用


fn longer<'a>(s1:&'a str, s2:&'a str)->&'a str{
    if s2.len()>s1.len(){
        s2
    } else {
        s1
    }
}

fn main(){
    let r;
    {
        let s1 = "rust";
        let s2 = "ecmascript";
        r = longer(s1, s2);
        println!("{} is longer", r);
    }

}

46. 生命周期2

结构体中使用字符串切片引用

// 结构体中使用字符串切片引用

fn main(){
    struct Str<'a>{
        content: &'a str
    }
    let s = Str{
        content: "string_slice"
    };
    println!("s.content={}", s.content);


}

47. 泛型 特性 和 生命周期的综合例子

// 泛型、特性与生命周期 一起来

use std::fmt::Display;


fn longest_with_an_announcement<'a, T>(x: &'a str, y: &'a str, ann: T)-> &'a str where T: Display{
    println!("Announcement! {}", ann);
    if x.len() > y.len(){
        x
    } else{
        y
    }
}

fn main(){
    let r = longest_with_an_announcement("abcd", "efg", "hello");
    println!("longest {}", r);
}

48. 接收命令行参数

// 接收命令行参数

fn main(){
    let args = std::env::args();
    println!("{:?}", args);
    // Args { inner: ["target\\debug\\greeting.exe"] }

    // 遍历
    for arg in args{
        // target\debug\greeting.exe
        println!("{}", arg);
    }

}

49. 从命令行传入字符串

// 命令行输入输入一些字母 IO流
use std::io::stdin;


fn main(){
    let mut str_buf = String::new();
    // 从命令行输入一些字符
    stdin().read_line(&mut str_buf).expect("failed to read line");
    println!("your input line is \n{}", str_buf);


}

50. 从文件读入

// 从文件读取字符
use std::fs;


fn main(){
    let text = fs::read_to_string("d:/hello.txt").unwrap();
    println!("{}", text);

}

51. 读取文件

整个文件一次性读取

// 从文件读取字符
use std::fs;


fn main(){
    let content = fs::read("D:/text.txt").unwrap();
    println!("{:?}", content);


}

52. IO流

// 流读取
use std::fs::{self, File};
use std::io::prelude::*;


fn main(){
    let mut buffer = [0u8; 5];
    let mut file = fs::File::open("d:/text.txt").unwrap();
    file.read(&mut buffer).unwrap();
    println!("{:?}", buffer);
    file.read(&mut buffer).unwrap();
    println!("{:?}", buffer);

}

53. 文件写入

use std::fs;


fn main(){
    // 文件写入
    fs::write("d:/text.txt", "FROM RUST PROGRAM").unwrap();
}

54. 文件末尾追加字符

use std::io::prelude::*;
use std::fs::OpenOptions;


fn main()->std::io::Result<()>{
    let mut file = OpenOptions::new().append(true).open("d:/text.txt")?;
    file.write(b" APPEND WORD");
    Ok(())
}

55. 读写方式打开文件


use std::io::prelude::*;
use std::fs::OpenOptions;


fn main()->std::io::Result<()>{
    
    let mut file = OpenOptions::new().read(true).write(true).open("d:/text.txt")?;
    file.write(b"COVER")?;
    Ok(())

}

56. 集合一

集合的创建

// 集合创建
fn main(){
    let vector: Vec<i32> = Vec::new(); // 创建类型为 i32 的空向量
    let vector = vec![1, 2, 4, 8]; // 通过数组创建向量

}

57. 向集合添加元素

使用push添加元素

// push 添加 元素
fn main(){
    let mut vector = vec![1, 2, 4, 8];
    vector.push(16);
    vector.push(32);
    vector.push(64);
    println!("{:?}", vector);

}

58. 在集合末尾添加一个集合

// append 添加集合
fn main(){
    let mut v1:Vec<i32> = vec![1, 2, 4, 8];
    let mut v2:Vec<i32> = vec![16, 32, 64];

    v1.append(&mut v2);
    println!("{:?}", v1);

}

59. 集合遍历和取元素


fn main(){
    let mut v = vec![1, 2, 4, 8];
    // 相对安全的取值方法
    println!("{}", match v.get(0) {
        Some(value)=>value.to_string(),
        None=>"None".to_string()
    });

    // 下标取值
    let v = vec![1, 2, 4, 8];
    println!("{}", v[1]);

    // 遍历
    let v = vec![100, 32, 57];
    for i in &v{
        println!("{}", i);
    }

}

60. string字符串操作


fn main(){
    // 新建字符串
    let string = String::new();
    // 基础类型转成字符串
    let ont = 1.to_string();
    let float = 1.3.to_string();
    let slice = "slice".to_string();
    //  包含 UTF-8 字符的字符串
    let hello = String::from("السلام عليكم");
    let hello = String::from("Dobrý den");
    let hello = String::from("Hello");
    let hello = String::from("שָׁלוֹם");
    let hello = String::from("नमस्ते");
    let hello = String::from("こんにちは");
    let hello = String::from("안녕하세요");
    let hello = String::from("你好");
    let hello = String::from("Olá");
    let hello = String::from("Здравствуйте");
    let hello = String::from("Hola");
    // 字符串追加
    let mut s = String::from("run");
    s.push_str("oob");
    s.push_str("!");

    // + 拼接字符串
    let s1 = String::from("Hello, ");
    let s2 = String::from("world!");
    let s3 = s1 + &s2;

    // 使用format!宏
    let s1 = String::from("tic");
    let s2 = String::from("tac");
    let s3 = String::from("toe");
    let s = format!("{}-{}-{}", s1, s2, s3);

    let s = "hello";
    let len = s.len();

    // 中文字符长度
    let s = "你好";
    let len = s.len(); // 6 中文utf-8编码,一个字长3个字节
    println!("{}", len);

    // 中文字符正确长度
    let s = "你好";
    let len = s.chars().count(); // 2
    println!("{}", len);

    // 字符串遍历
    let s = String::from("hello中文");
    for c in s.chars(){
        println!("{}", c);
    }

    // 取单个字符
    let s = String::from("EN中文");
    let a = s.chars().nth(2); // Some('中')
    println!("{:?}", a); 

    // 按索引截取字符串 不推荐 遇到中文有问题
    let s = String::from("EN中文"); 
    let sub = &s[0..2]; // EN
    // let sub = &s[0..3]; // 报错了
    println!("{}", sub);



}

61. hashmap

use std::collections::HashMap;


fn main(){
    // 映射表操作
    let mut map = HashMap::new();

    map.insert("color", "red");
    map.insert("size", "10 m^2");
    println!("{}", map.get("color").unwrap());

    // 遍历映射表操作
    for p in map.iter(){
        println!("{:?}", p);
        /*
        ("color", "red")
        ("size", "10 m^2")
         */
    }

    // 先判断key是否存在,然后才安全插入
    map.entry("color").or_insert("red");

    let mut map = HashMap::new();
    map.insert(1, "a");
    // 在已经确定有某个键的情况下直接修改对应的值
    if let Some(x) = map.get_mut(&1){
        *x = "b";
    }

    for p in map.iter(){
        println!("{:?}", p);
    }
    // (1, "b")


}

62. 面向对象

second.rs

pub struct ClassName{
    field: i32,
}

impl ClassName{
    pub fn new(value: i32)->ClassName{
        ClassName{
            field: value
        }
    }

    pub fn public_method(&self){
        println!("from public method");
        self.private_method();
    }

    fn private_method(&self){
        println!("from private method");
    }

}

main.rs

mod second;
use second::ClassName;


fn main(){
    let object = ClassName::new(1024);
    object.public_method();

}

63. 并发编程1

use std::thread;
use std::time::Duration;

fn spawn_function(){
    for i in 0..5{
        println!("spawned thread print {}", i);
        thread::sleep(Duration::from_millis(1));
    }
}

fn main(){
    thread::spawn(spawn_function);
    for i in 0..3{
        println!("main thread print {}", i);
        thread::sleep(Duration::from_millis(1));
    }
}

64. 并发编程2 匿名函数

use std::thread;
use std::time::Duration;


fn main(){
    // 闭包是可以保存进变量或作为参数传递给其他函数的匿名函数。闭包相当于 Rust 中的 Lambda 表达式,格式如下:
    /**

    |参数1, 参数2, ...| -> 返回值类型 {
    // 函数体
    }

     */
    
    thread::spawn(||{
        for i in 0..5 {
            println!("spawned thread print {}", i);
            thread::sleep(Duration::from_millis(1));
        }
    });

    for i in 0..3 {
        println!("main thread print {}", i);
        thread::sleep(Duration::from_millis(1));
    }


}



65. 匿名函数与参数传递

fn main(){
    // 匿名函数与参数传递
    let inc = |num: i32|->i32{
        num + 1
    };
    println!("inc(5) = {}", inc(5));

    let inc = |num|{
        num + 1
    };
    println!("inc(5) = {}", inc(5));


}

66. 守护线程

use std::thread;
use std::time::Duration;


// join 方法可以使子线程运行结束后再停止运行程序。
fn main(){
    let handle = thread::spawn(||{
        for i in 0..5{
            println!("spawned thread print {}", i);
            thread::sleep(Duration::from_millis(1));
        }
    });

    for i in 0..3{
        println!("main thread print {}", i);
        thread::sleep(Duration::from_millis(1));
    }

    handle.join().unwrap();
    /*
       main thread print 0
        spawned thread print 0
        main thread print 1
        spawned thread print 1
        spawned thread print 2
        main thread print 2
        spawned thread print 3
        spawned thread print 4
     */

}

67. 使用move进行所有权迁移

使用move让子线程访问主线程变量

use std::thread;

fn main() {
    let s = "hello";
    
    let handle = thread::spawn(move || {
        println!("{}", s);
    });

    handle.join().unwrap();
}

68. 主线程与子线程之间的消息收发

// 消息传递
use std::thread;
use std::sync::mpsc;


fn main(){
    let (tx, rx) = mpsc::channel();
    
    thread::spawn(move||{
        let val = String::from("hi");
        tx.send(val).unwrap();
    });

    let received = rx.recv().unwrap();
    println!("Got: {}", received);


}

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