rustlings 学习笔记 -- exercises/07_structsexercises/07_structs s

exercises/07_structs

structs1.rs - 结构体基础类型

问题代码

struct ColorRegularStruct {
    // TODO: Add the fields that the test `regular_structs` expects.
    // What types should the fields have? What are the minimum and maximum values for RGB colors?
}

struct ColorTupleStruct(/* TODO: Add the fields that the test `tuple_structs` expects */);

#[derive(Debug)]
struct UnitStruct;

fn main() {
    // You can optionally experiment here.
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn regular_structs() {
        // TODO: Instantiate a regular struct.
        // let green =

        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 =

        assert_eq!(green.0, 0);
        assert_eq!(green.1, 255);
        assert_eq!(green.2, 0);
    }

    #[test]
    fn unit_structs() {
        // TODO: Instantiate a unit struct.
        // let unit_struct =
        let message = format!("{unit_struct:?}s are fun!");

        assert_eq!(message, "UnitStructs are fun!");
    }
}

解题要点

错误原因: 缺少结构体字段定义和实例化代码
解决方法: 定义 RGB 颜色字段并创建结构体实例

正确写法

struct ColorRegularStruct {
    red: u8,
    green: u8,
    blue: u8,
}

struct ColorTupleStruct(u8, u8, u8);

#[derive(Debug)]
struct UnitStruct;

fn main() {
    // You can optionally experiment here.
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn regular_structs() {
        let green = ColorRegularStruct {
            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() {
        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() {
        let unit_struct = UnitStruct;
        let message = format!("{unit_struct:?}s are fun!");

        assert_eq!(message, "UnitStructs are fun!");
    }
}

structs2.rs - 结构体更新语法

问题代码

#[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,
    }
}

fn main() {
    // You can optionally experiment here.
}

#[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 =

        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);
    }
}

解题要点

错误原因: 缺少使用更新语法创建新结构体实例
解决方法: 使用 ..template 语法复制其他字段

正确写法

#[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,
    }
}

fn main() {
    // You can optionally experiment here.
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn your_order() {
        let order_template = create_order_template();

        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);
    }
}

structs3.rs - 结构体方法

问题代码

#[derive(Debug)]
struct Package {
    sender_country: String,
    recipient_country: String,
    weight_in_grams: u32,
}

impl Package {
    fn new(sender_country: String, recipient_country: String, weight_in_grams: u32) -> Self {
        if weight_in_grams < 10 {
            panic!("Can't ship a package with weight below 10 grams");
        }

        Self {
            sender_country,
            recipient_country,
            weight_in_grams,
        }
    }

    // TODO: Add the correct return type to the function signature.
    fn is_international(&self) {
        // TODO: Read the tests that use this method to find out when a package
        // is considered international.
    }

    // TODO: Add the correct return type to the function signature.
    fn get_fees(&self, cents_per_gram: u32) {
        // TODO: Calculate the package's fees.
    }
}

fn main() {
    // You can optionally experiment here.
}

#[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, 5);
    }

    #[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);
    }
}

解题要点

错误原因: 缺少方法返回类型和实现逻辑
解决方法: 添加返回类型并实现国际包裹判断和费用计算

正确写法

#[derive(Debug)]
struct Package {
    sender_country: String,
    recipient_country: String,
    weight_in_grams: u32,
}

impl Package {
    fn new(sender_country: String, recipient_country: String, weight_in_grams: u32) -> Self {
        if weight_in_grams < 10 {
            panic!("Can't ship a package with weight below 10 grams");
        }

        Self {
            sender_country,
            recipient_country,
            weight_in_grams,
        }
    }

    fn is_international(&self) -> bool {
        self.sender_country != self.recipient_country
    }

    fn get_fees(&self, cents_per_gram: u32) -> u32 {
        self.weight_in_grams * cents_per_gram
    }
}

fn main() {
    // You can optionally experiment here.
}

#[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, 5);
    }

    #[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);
    }
}

知识点汇总

结构体类型

常规结构体: 具有命名字段的结构体，如 struct Name { field: Type }
元组结构体: 类似元组的结构体，使用索引访问字段，如 struct Name(Type1, Type2)
单元结构体: 没有字段的结构体，如 struct Name;

结构体操作

实例化: 使用字段名初始化常规结构体，使用元组语法初始化元组结构体
更新语法: 使用 ..template 语法从现有结构体创建新实例
字段访问: 常规结构体使用点号和字段名，元组结构体使用索引

结构体方法

关联函数: 使用 impl 块定义函数，new 函数用于创建实例
方法: 第一个参数为 &self 的函数，用于操作结构体数据
返回类型: 方法必须显式指定返回类型