#[derive(Debug)] 做了什么
- 加上#[derive(Debug)]属性时，编译器会自动为这个类型生成 Debug特征的实现代码。
-
- 就可以使用 println!(“{:?}”, your_variable) 或者 dbg!(your_variable) 这样的语句来打印出该变量的详细信息了。
#[derive(Debug)]
struct Point {x: i32,y: i32,
}fn main() {let p = Point { x: 10, y: 20 };println!("{:?}", p);
}
#[derive(Debug)]
struct Rectangle {width: u32,length: u32,
}
// 结构体 实现方法
impl Rectangle {// 传入引用的 结构体fn area(&self) -> u32 {self.width * self.length}fn can_hold(&self, other: &Rectangle) -> bool {self.width >= other.width && self.length >= other.length}
}
fn main() {let rect1: Rectangle = Rectangle {width: 30,length: 50,};let rect2: Rectangle = Rectangle {width: 10,length: 50,};let rect3: Rectangle = Rectangle {width: 40,length: 50,};println!("{}", rect1.can_hold(&rect2));println!("{}", rect1.can_hold(&rect3));println!("{}", rect1.area());println!("{:#?}", rect1);
}
#[derive(Debug)]
struct Rectangle {width: u32,length: u32,
}
// 结构体 实现方法
impl Rectangle {// 传入引用的 结构体fn area(&self) -> u32 {self.width * self.length}fn can_hold(&self, other: &Rectangle) -> bool {self.width >= other.width && self.length >= other.length}// 关联函数fn square(size: u32) -> Rectangle {Rectangle {width: size,length: size,}}
}
fn main() {let rect1: Rectangle = Rectangle {width: 30,length: 50,};let rect2: Rectangle = Rectangle {width: 10,length: 50,};let rect3: Rectangle = Rectangle {width: 40,length: 50,};// 调用关联方法let s1: Rectangle = Rectangle::square(32);println!("{}", rect1.can_hold(&rect2));println!("{}", rect1.can_hold(&rect3));println!("{}", rect1.area());println!("{:#?}", rect1);println!("{:#?}", s1);
}
println!(“{:#?}”, s1);
这个看里面几个特殊字符有什么意义
- {}这是格式化输出的占位符
- #当与格式化输出的 {} 结合使用{:#?} 这种形式相比于 {:?} 会让输出的格式更 “美观”、易读，呈现出更有层次结构的缩进格式，便于查看复杂数据结构内部详细的成员信息等
- ? 在格式化输出的上下文中，与 {} 配合使用时用于告诉 Rust 编译器按照实现的 Debug 特性的要求来格式化输出对应的值。
enum IpAddrKind {v4(u8, u8, u8, u8),v6(String),
}fn main() {let home = IpAddrKind::v4(127, 0, 0, 1);let loopback = IpAddrKind::v6(String::from("::1"));
}
#[derive(Debug)]
enum IpAddrKind {v4(u8, u8, u8, u8),v6(String),
}
impl IpAddrKind {fn ping(&self) {println!("{:?}", self)}
}
fn main() {let home = IpAddrKind::v4(127, 0, 0, 1);let loopback = IpAddrKind::v6(String::from("::1"));home.ping();
}
fn main() {let some_number = Some(5);let some_string = Some("slice str");let absent_number: Option<i32> = None;
}
enum Coin {Penny,Nickel,Dime,Quarter,
}fn value_in_cents(coin: Coin) -> u32 {match coin {Coin::Penny => 1,Coin::Nickel => 5,Coin::Dime => 10,Coin::Quarter => 25,}
}fn main() {value_in_cents(Coin::Dime);
}
#[derive(Debug)]
enum Coin {Penny,Nickel,Dime,Quarter,
}fn value_in_cents(coin: Coin) -> u32 {match coin {Coin::Penny => 1,Coin::Nickel => 5,Coin::Dime => {println!("{:#?}", coin);1}Coin::Quarter => 25,}
}fn main() {value_in_cents(Coin::Dime);
}
#[derive(Debug)]
enum UsState {Alabama,Alaska,Arizona,Arkansas,California,Colorado,Connecticut,Delaware,Florida,Georgia,Hawaii,Idaho,Illinois,Indiana,Iowa,Kansas,Kentucky,Louisiana,Maine,Maryland,Massachusetts,Michigan,Minnesota,Mississippi,Missouri,Montana,Nebraska,Nevada,NewHampshire,NewJersey,NewMexico,NewYork,NorthCarolina,NorthDakota,Ohio,Oklahoma,Oregon,Pennsylvania,RhodeIsland,SouthCarolina,SouthDakota,Tennessee,Texas,Utah,Vermont,Virginia,Washington,WestVirginia,Wisconsin,Wyoming,
}enum Coin {Penny,Nickel,Dime,Quarter(UsState),
}fn value_in_cents(coin: Coin) -> u32 {match coin {Coin::Dime => 1,Coin::Nickel => 5,Coin::Penny => 10,Coin::Quarter(state) => {println!("{:#?}", state);25}}
}fn main() {value_in_cents(Coin::Quarter(UsState::Alabama));
}
