【Rust】可选枚举（一）

环境

• Time 2022-03-25
• Rust 1.59.0

示例

is_some

fn main() {
    let name = Some("JiangBo");
    println!("{:?}", name.is_some());
}

is_none

fn main() {
    let name = Some("JiangBo");
    println!("{:?}", name.is_none());
}

as_ref

fn main() {
    let name = Some("JiangBo".to_owned());
    println!("{:?}", name.as_ref().map(|e| e.len()));
    println!("{:?}", name);
}

as_mut

fn main() {
    let mut name = Some("JiangBo".to_owned());
    name.as_mut().map(|e| e.push('!')).unwrap();
    println!("{:?}", name);
}

expect

fn main() {
    let name = Some("JiangBo");
    println!("{:?}", name.expect("Error"));
}

unwrap

fn main() {
    let name = Some("JiangBo");
    println!("{:?}", name.unwrap());
}

unwrap_or

fn main() {
    let name: Option<&str> = None;
    println!("{:?}", name.unwrap_or("Rust"));
}

unwrap_or_else

fn main() {
    let age: Option<i32> = None;
    println!("{:?}", age.unwrap_or_else(|| 2 * 4));
}

unwrap_or_default

fn main() {
    let age: Option<i32> = None;
    println!("{:?}", age.unwrap_or_default());
}

总结

了解了可选枚举中相关的一些方法。

附录