如何将字符串的值限制为 Rust 中的某个集合?
// string literal union type with
// values of "admin", "owner", "user"
type Roles = "admin" | "owner" | "user";
// use the type "Roles" for the "role" variable
let role: Roles;
// assing a value other than "admin", "owner", "user"
role = "Hello World!"; // ❌ not allowed. Type '"Hello World!"' is not assignable to type 'Roles'
// assign a valid string value
role = "admin"; // ✅ allowed.
rust 的等价物是什么
您可以为您的角色使用
enum
,然后使用序列化方法(例如使用 strum
或 serde
)来解析任何字符串输入并验证它们是否可以应用。
这是一个使用扫弦的示例:
use std::str::FromStr;
use strum_macros::EnumString;
#[derive(Debug, PartialEq, EnumString)]
#[strum(ascii_case_insensitive)]
enum Role {
Admin,
Owner,
User,
}
// tests
let admin = Role::from_str("admin").unwrap();
assert_eq!(Role::Admin, admin);
接受的答案指出了正确的方向,但在细节上有点缺乏。
首先安装
strum
所需的功能:
cargo add strum --features derive,strum_macros
在
enum
中定义字符串(注意,使用自定义 serialize
属性,您可以输入所需的任何字符串格式):
#[derive(Debug, PartialEq, EnumString, strum::Display)]
enum Role {
#[strum(serialize = "admin")]
Admin,
#[strum(serialize = "Owner")]
Owner,
#[strum(serialize = "regular user")]
User,
#[strum(serialize = "GUEST")]
Guest,
}
要从字符串转换为枚举,它依赖于 FromStr 特征 (
use std::str::FromStr
):
let admin = Role::from_str("admin").unwrap();
assert_eq!(Role::Admin, admin);
let owner = Role::from_str("Owner").unwrap();
assert_eq!(Role::Owner, owner);
let user = Role::from_str("regular user").unwrap();
assert_eq!(Role::User, user);
let guest = Role::from_str("GUEST").unwrap();
assert_eq!(Role::Guest, guest);
从枚举转换为字符串 (
strum::Display
):
let admin_str = Role::Admin.to_string();
assert_eq!("admin", admin_str);
let owner_str = Role::Owner.to_string();
assert_eq!("Owner", owner_str);
let user_str = Role::User.to_string();
assert_eq!("regular user", user_str);
let guest_str = Role::Guest.to_string();
assert_eq!("GUEST", guest_str);