【rCore OS 开源操作系统】Rust 练习题题解: Structs
摘要
rCore OS 开源操作系统训练营学习中的代码练习部分。
在此记录下自己学习过程中的产物，以便于日后更有"收获感"。
后续还会继续完成其他章节的练习题题解。
正文
structs1
题目
rust
// 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
}
struct ColorTupleStruct(
/* TODO: Something goes here */
);
#[derive(Debug)]
struct UnitLikeStruct;
#[cfg(test)]
mod tests {
use super::*;
#[test]
fn classic_c_structs() {
// TODO: Instantiate a classic c 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-like struct!
// let unit_like_struct =
let message = format!("{:?}s are fun!", unit_like_struct);
assert_eq!(message, "UnitLikeStructs are fun!");
}
}题解
structs 的基本如下：
rust
// 定义
struct User {
age: i32,
active: bool,
username: String,
email: String,
sign_in_count: u64,
}
// 实现方法
impl User{
fn info(&self) -> i32 {
&self.age + 1 // 不加分号，就是 tail exp, 自带 return
}
}
// 实例化
let rect1 = Rectangle {
width: 30,
height: 50,
};
rect1.area()
// 元组结构体定义
struct User2(i32, i32, i32);
let user = User2(1, 1, 1);
// 类单元结构体定义
struct User3;
let user3 = User3;所以答案也就是呼之欲出了：
rust
// structs1.rs
//
// Address all the TODOs to make the tests pass!
//
// Execute `rustlings hint structs1` or use the `hint` watch subcommand for a
// hint.
struct ColorClassicStruct {
// TODO: Something goes here
red: i32,
green: i32,
blue: i32,
}
struct ColorTupleStruct(/* TODO: Something goes here */ i32, i32, i32);
#[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!");
}
}Structs2
题目
rust
// 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 =
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);
}
}解析
第二章节主要是考察结构体方法的实现。
这里提到的update语法，是类似 JS 中的对象展开+字段覆盖的操作。
但是这里的覆盖是有固定优先级的，和字段书写顺序无关
rust
// structs2.rs
//
// Address all the TODOs to make the tests pass!
//
// Execute `rustlings hint structs2` or use the `hint` watch subcommand for a
// hint.
#[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);
}
}Structs3
题目
rust
// 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) -> ??? {
// Something goes here...
}
fn get_fees(&self, cents_per_gram: i32) -> ??? {
// Something goes 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, -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);
}
}解析
根据意思，补全结构体的方法实现，对比是否为同一个地区，判断是否相同，以及计算费用，比较简单。
rust
// 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.
#[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...
&self.sender_country != &self.recipient_country
}
fn get_fees(&self, cents_per_gram: i32) -> i32 {
// Something goes here...
&self.weight_in_grams * cents_per_gram
}
}
#[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);
}
}