rust 学习 match专项

fn main() { let x 8; // 定义 x match x { 0 println!(零), 1|2|3 println!( 1 or 2 or 3), 4..6 println!(4-6), n println!(其他数字: {}, n), } let tuple (1, 2, 3,4); match tuple { (1, 2,..) println!(第一个是 1), _ (), } let arr [1, 2, 3]; match arr { [0, _, _] println!(第一个是 0), [a, b, c] println!({},{},{}, a, b, c), _ (), } let point (10, 20); match point { (0, 0) println!(原点), (x, 0) println!(x 轴: {}, x), (0, y) println!(y 轴: {}, y), (x, y) println!(坐标: ({}, {}), x, y), } #[derive(Debug)] struct Point { x: i32, y: i32 } let p1 Point { x: 0, y: 0 }; match p1 { Point { x: 0, y: 0 } println!(原点), Point { x, y } if x y println!(对角线), Point { x, y } println!(({}, {}), x, y), } enum Message { Quit, Move { x: i32, y: i32 }, Write(String), ChangeColor(u8, u8, u8), } let msg Message::Move { x: 10, y: 20 }; match msg { Message::Quit println!(退出), Message::Move { x, y } println!(移动到 ({}, {}), x, y), Message::Write(text) println!(消息: {}, text), Message::ChangeColor(r, g, b) println!(RGB: {},{},{}, r, g, b), } let num Some(5); match num { Some(x) println!(解引用后: {}, x), // 直接取值 // 或者 Some(ref x) println!(借用: {}, x), // ref 表示引用 None (), } match x { 7 | 8 if x % 2 0 println!(7 或 8 且为偶数), n if n 0 println!(负数), n if n 0 println!(零), n if n 0 println!(正数), _ (), } //所有分支必须返回相同类型 let result match x { 0 零.to_string(), n format!(其他: {}, n), }; println!({}, result); //绑定运算符 match x { n 1..5 println!(1~5: {}, n), n 6..10 println!(6~10: {}, n), _ println!(其他), } match p1 { p Point { x: 0, y: 0 } println!(原点: {:?}, p), _ (), } if let Some(value) Some(5){ //if let Some(value) Option::i32::None println!(有值: {}, value); } else { println!(无值); } let result: Resulti32, str Err(error); if let Ok(value) result { println!(成功: {}, value); } else { println!(失败); } let mut stack vec![1, 2, 3, 4, 5]; while let Some(top) stack.pop() { println!(弹出: {}, top);// 输出5 4 3 2 1 } } //实战综合示例 use std::fs::File; use std::io::Read; fn main() { // 处理 Option let ages: VecOptioni32 vec![Some(10), None, Some(25)]; for age in ages { if let Some(age) age { if age 18 { println!(未成年: {}, age); } else { println!(成年: {}, age); } } else { println!(年龄未知); } } // 处理 Result let mut file File::open(test.txt); if let Ok(mut f) file { let mut content String::new(); if let Ok(_) f.read_to_string(mut content) { println!(文件内容: {}, content); } else { println!(读取失败); } } else { println!(文件不存在); } // 枚举匹配 #[derive(Debug)] enum UserAction { Create(String), Delete(i32), Update { id: i32, name: String }, } let action UserAction::Create(Alice.to_string()); if let UserAction::Create(name) action { println!(创建用户: {}, name); } }