环境
- Rust 1.56.1
- VSCode 1.61.2
概念
参考：https://doc.rust-lang.org/stable/rust-by-example/flow_control/match/guard.html
示例
条件过滤
fn main() {
let pair = (2, 2);
println!("Tell me about {:?}", pair);
match pair {
// if 就是保护语句，可以进行条件过滤
(x, y) if x == y => println!("These are twins"),
(x, y) if x + y == 0 => println!("Antimatter, kaboom!"),
(x, _) if x % 2 == 1 => println!("The first one is odd"),
_ => println!("No correlation..."),
}
}
匹配所有
fn main() {
let number: u8 = 4;
match number {
i if i == 0 => println!("Zero"),
i if i > 0 => println!("Greater than zero"),
// 编译器不会检查条件是否覆盖完全，需要加上全匹配
_ => println!("Fell through"),
}
}
总结
了解了 Rust 中的匹配保护，也就是匹配的条件过滤。