RustDay05------Exercise[31-40]

31.结构体申明

结构体在这里给了三种声明样式

(1)字典样式的键值对(使用花括号)

(2)元组样式的数值元组(使用圆括号)

(3)空结构体,可以被格式化输出名字

// structs1.rs
// Address all the TODOs to make the tests pass!
// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
struct ColorClassicStruct {
    // TODO: Something goes here
    red:u8,
    green:u8,
    blue:u8,
}
 
struct ColorTupleStruct(u8,u8,u8);
 
#[derive(Debug)]
struct UnitLikeStruct;
 
#[cfg(test)]
mod tests {
    use super::*;
 
    #[test]
    fn classic_c_structs() {
        // TODO: Instantiate a classic c struct!
        let green =ColorClassicStruct{red:0,green:255,blue:0};
 
        assert_eq!(green.red, 0);
        assert_eq!(green.green, 255);
        assert_eq!(green.blue, 0);
    }
 
    #[test]
    fn tuple_structs() {
        // TODO: Instantiate a tuple struct!
        let green =ColorTupleStruct(0,255,0);
 
        assert_eq!(green.0, 0);
        assert_eq!(green.1, 255);
        assert_eq!(green.2, 0);
    }
 
    #[test]
    fn unit_structs() {
        // TODO: Instantiate a unit-like struct!
        let unit_like_struct =UnitLikeStruct;
        let message = format!("{:?}s are fun!", unit_like_struct);
 
        assert_eq!(message, "UnitLikeStructs are fun!");
    }
}

32.结构体的解包

我们可以在一个结构体实例里面使用..otherStruct来对otherStruct里面未被定义的变量原封不动解包到该结构体实例里面

// structs2.rs
// Address all the TODOs to make the tests pass!
// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
#[derive(Debug)]
struct Order {
    name: String,
    year: u32,
    made_by_phone: bool,
    made_by_mobile: bool,
    made_by_email: bool,
    item_number: u32,
    count: u32,
}
 
fn create_order_template() -> Order {
    Order {
        name: String::from("Bob"),
        year: 2019,
        made_by_phone: false,
        made_by_mobile: false,
        made_by_email: true,
        item_number: 123,
        count: 0,
    }
}
 
#[cfg(test)]
mod tests {
    use super::*;
 
    #[test]
    fn your_order() {
        let order_template = create_order_template();
        // TODO: Create your own order using the update syntax and template above!
        let your_order = Order{
            name: String::from("Hacker in Rust"),
            count:1,
            ..order_template
        };
        assert_eq!(your_order.name, "Hacker in Rust");
        assert_eq!(your_order.year, order_template.year);
        assert_eq!(your_order.made_by_phone, order_template.made_by_phone);
        assert_eq!(your_order.made_by_mobile, order_template.made_by_mobile);
        assert_eq!(your_order.made_by_email, order_template.made_by_email);
        assert_eq!(your_order.item_number, order_template.item_number);
        assert_eq!(your_order.count, 1);
    }
}

33.类里面的方法除了当前区域内的变量,其他都要加self引用

// structs3.rs
// Structs contain data, but can also have logic. In this exercise we have
// defined the Package struct and we want to test some logic attached to it.
// Make the code compile and the tests pass!
// Execute `rustlings hint structs3` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
#[derive(Debug)]
struct Package {
    sender_country: String,
    recipient_country: String,
    weight_in_grams: i32,
}
 
impl Package {
    fn new(sender_country: String, recipient_country: String, weight_in_grams: i32) -> Package {
        if weight_in_grams <= 0 {
            panic!("Can not ship a weightless package.")
        } else {
            Package {
                sender_country,
                recipient_country,
                weight_in_grams,
            }
        }
    }
 
    fn is_international(&self) -> bool {
        // Something goes here...
        return self.sender_country!=self.recipient_country
    }
 
    fn get_fees(&self, cents_per_gram: i32) -> i32 {
        // Something goes here...
        return cents_per_gram*self.weight_in_grams
    }
}
 
#[cfg(test)]
mod tests {
    use super::*;
 
    #[test]
    #[should_panic]
    fn fail_creating_weightless_package() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Austria");
 
        Package::new(sender_country, recipient_country, -2210);
    }
 
    #[test]
    fn create_international_package() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Russia");
 
        let package = Package::new(sender_country, recipient_country, 1200);
 
        assert!(package.is_international());
    }
 
    #[test]
    fn create_local_package() {
        let sender_country = String::from("Canada");
        let recipient_country = sender_country.clone();
 
        let package = Package::new(sender_country, recipient_country, 1200);
 
        assert!(!package.is_international());
    }
 
    #[test]
    fn calculate_transport_fees() {
        let sender_country = String::from("Spain");
        let recipient_country = String::from("Spain");
 
        let cents_per_gram = 3;
 
        let package = Package::new(sender_country, recipient_country, 1500);
 
        assert_eq!(package.get_fees(cents_per_gram), 4500);
        assert_eq!(package.get_fees(cents_per_gram * 2), 9000);
    }
}

34.添加枚举类型以供打印

// enums1.rs
// No hints this time! ;)
 
// I AM NOT DONE
 
#[derive(Debug)]
enum Message {
    // TODO: define a few types of messages as used below
    Quit,
    Echo,
    Move,
    ChangeColor,
}
 
fn main() {
    println!("{:?}", Message::Quit);
    println!("{:?}", Message::Echo);
    println!("{:?}", Message::Move);
    println!("{:?}", Message::ChangeColor);
}

35.对枚举类型实现方法

使用向enumeration type添加一个方法

// enums2.rs
// Execute `rustlings hint enums2` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
#[derive(Debug)]
enum Message {
    // TODO: define the different variants used below
    Move { x: i32, y: i32 },
    Echo(String),
    ChangeColor(u8, u8, u8),
    Quit,
}
// impl用于向一个类型（可以是结构体、枚举、特质 trait 等）添加方法或实现 trait，从而为该类型定义特定的行为。
impl Message {
    fn call(&self) {
        println!("{:?}", &self);
    }
}
 
fn main() {
    let messages = [
        Message::Move { x: 10, y: 30 },
        Message::Echo(String::from("hello world")),
        Message::ChangeColor(200, 255, 255),
        Message::Quit,
    ];
 
    for message in &messages {
        message.call();
    }
}

36.使用match对枚举类型的方法进行匹配

match 匹配格式如下

match vailableType {
    namespace1::fun1(args1,args2) => {
        return self.fun1(args1,args2)
    }
}

// enums3.rs
// Address all the TODOs to make the tests pass!
// Execute `rustlings hint enums3` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
enum Message {
    // TODO: implement the message variant types based on their usage below
    ChangeColor((u8,u8,u8)),
    Echo(String),
    Move(Point ),
    Quit,
    // state.process(Message::ChangeColor((255, 0, 255)));
    //     state.process(Message::Echo(String::from("hello world")));
    //     state.process(Message::Move(Point { x: 10, y: 15 }));
    //     state.process(Message::Quit);
}
 
struct Point {
    x: u8,
    y: u8,
}
 
struct State {
    color: (u8, u8, u8),
    position: Point,
    quit: bool,
}
 
impl State {
    fn change_color(&mut self, color: (u8, u8, u8)) {
        self.color = color;
    }
 
    fn quit(&mut self) {
        self.quit = true;
    }
 
    fn echo(&self, s: String) {
        println!("{}", s);
    }
 
    fn move_position(&mut self, p: Point) {
        self.position = p;
    }
 
    fn process(&mut self, message: Message) {
        // TODO: create a match expression to process the different message variants
        match message {
            Message::ChangeColor(objects) => {
                return self.change_color((objects.0,objects.1,objects.2))
            }
            Message::Echo(string) => {
                return self.echo(string)
            }
            Message::Move(point) => {
                return self.move_position( point)
            }
            Message::Quit => {
                return self.quit()
            }
            
        }
    }
}
 
#[cfg(test)]
mod tests {
    use super::*;
 
    #[test]
    fn test_match_message_call() {
        let mut state = State {
            quit: false,
            position: Point { x: 0, y: 0 },
            color: (0, 0, 0),
        };
        state.process(Message::ChangeColor((255, 0, 255)));
        state.process(Message::Echo(String::from("hello world")));
        state.process(Message::Move(Point { x: 10, y: 15 }));
        state.process(Message::Quit);
 
        assert_eq!(state.color, (255, 0, 255));
        assert_eq!(state.position.x, 10);
        assert_eq!(state.position.y, 15);
        assert_eq!(state.quit, true);
    }
}

37.将&str转成String

可以调用&str对象的to_string()方法或者使用String::from(&str)将其转换

// strings1.rs
// Make me compile without changing the function signature!
// Execute `rustlings hint strings1` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
fn main() {
    let answer = current_favorite_color();
    println!("My current favorite color is {}", answer);
}
 
fn current_favorite_color() -> String {
    String::from("blue")
}

38.在比较情况下,Sring和&str会隐式转化去比较

试运行如下代码:

fn main() {
    let string1 = "aaaa".to_string();
    let string2 = "aaaa";
 
    if string1 == string2 {
        println!("Strings are equal");
    } else {
        println!("Strings are not equal");
    }
}
//输出 Strings are equal

// strings2.rs
// Make me compile without changing the function signature!
// Execute `rustlings hint strings2` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
fn main() {
    let word = String::from("green"); // Try not changing this line :)
    if is_a_color_word(word) {
        println!("That is a color word I know!");
    } else {
        println!("That is not a color word I know.");
    }
}
 
fn is_a_color_word(attempt: String) -> bool {
    //对象类型不一致 都返回false
    // attempt == "green" || attempt == "blue" || attempt == "red"
    // let attempt = attempt.to_string();
    println!("{}|{}|{}",attempt == "green" ,attempt == "blue" ,attempt == "red");
    attempt == "green" || attempt == "blue" || attempt == "red"
 
}

39.&str类型清除两边空白与&str的replace

通常情况下&str使用方法后都会变成String

// strings3.rs
// Execute `rustlings hint strings3` or use the `hint` watch subcommand for a hint.
 
// I AM NOT DONE
 
fn trim_me(input: &str) -> String {
    // TODO: Remove whitespace from both ends of a string!
    input.trim().to_string()
}
 
fn compose_me(input: &str) -> String {
    // TODO: Add " world!" to the string! There's multiple ways to do this!
    input.trim().to_string()+" world!"
}
 
fn replace_me(input: &str) -> String {
    // TODO: Replace "cars" in the string with "balloons"!
    input.replace("cars","balloons")
}
 
#[cfg(test)]
mod tests {
    use super::*;
 
    #[test]
    fn trim_a_string() {
        assert_eq!(trim_me("Hello!     "), "Hello!");
        assert_eq!(trim_me("  What's up!"), "What's up!");
        assert_eq!(trim_me("   Hola!  "), "Hola!");
    }
 
    #[test]
    fn compose_a_string() {
        assert_eq!(compose_me("Hello"), "Hello world!");
        assert_eq!(compose_me("Goodbye"), "Goodbye world!");
    }
 
    #[test]
    fn replace_a_string() {
        assert_eq!(replace_me("I think cars are cool"), "I think balloons are cool");
        assert_eq!(replace_me("I love to look at cars"), "I love to look at balloons");
    }
}

40.&在调用方法和函数之后会变成哪些类型

看看就好,记住中间保持&str的特例函数和切片(trim()函数和切片变成&str)

// strings4.rs
 
// Ok, here are a bunch of values-- some are `String`s, some are `&str`s. Your
// task is to call one of these two functions on each value depending on what
// you think each value is. That is, add either `string_slice` or `string`
// before the parentheses on each line. If you're right, it will compile!
// No hints this time!
 
// I AM NOT DONE
 
fn string_slice(arg: &str) {
    println!("{}", arg);
}
fn string(arg: String) {
    println!("{}", arg);
}
 
fn main() {
    string_slice("blue");
    string("red".to_string());
    string(String::from("hi"));
    string("rust is fun!".to_owned());
    string("nice weather".into());
    string(format!("Interpolation {}", "Station"));
    string_slice(&String::from("abc")[0..1]);
    string_slice("  hello there ".trim());
    string("Happy Monday!".to_string().replace("Mon", "Tues"));
    string("mY sHiFt KeY iS sTiCkY".to_lowercase());
}