typescript 字符串枚举的反向映射
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Reverse-Mapping for String Enums
提问by Kamyar Ghajar
I wanted to use string enums in typescript but I can't see a support for reversed mapping in it. I have an enum like this:
我想在打字稿中使用字符串枚举，但我看不到它支持反向映射。我有一个这样的枚举：
enum Mode {
Silent = "Silent",
Normal = "Normal",
Deleted = "Deleted"
}
and I need to use it like this:
我需要像这样使用它：
let modeStr: string;
let mode: Mode = Mode[modeStr];
and yes I don't know what is it there in modeStrstring and I need it parsed to the enum or a fail at parsing in runtime if the string is not presented in the enum definition.
How can I do that as neat as it can be?
thanks in advance
是的，我不知道modeStr字符串中有什么，如果字符串未出现在枚举定义中，我需要将其解析为枚举或在运行时解析失败。我怎样才能做到尽可能整洁？提前致谢
采纳答案by Rodris
We can make the Modeto be a type and a value at the same type.
我们可以使Mode成为一个类型和一个相同类型的值。
type Mode = string;
let Mode = {
Silent: "Silent",
Normal: "Normal",
Deleted: "Deleted"
}
let modeStr: string = "Silent";
let mode: Mode;
mode = Mode[modeStr]; // Silent
mode = Mode.Normal; // Normal
mode = "Deleted"; // Deleted
mode = Mode["unknown"]; // undefined
mode = "invalid"; // "invalid"
A more strict version:
更严格的版本：
type Mode = "Silent" | "Normal" | "Deleted";
const Mode = {
get Silent(): Mode { return "Silent"; },
get Normal(): Mode { return "Normal"; },
get Deleted(): Mode { return "Deleted"; }
}
let modeStr: string = "Silent";
let mode: Mode;
mode = Mode[modeStr]; // Silent
mode = Mode.Normal; // Normal
mode = "Deleted"; // Deleted
mode = Mode["unknown"]; // undefined
//mode = "invalid"; // Error
String Enum as this answer:
字符串枚举作为这个答案：
enum Mode {
Silent = <any>"Silent",
Normal = <any>"Normal",
Deleted = <any>"Deleted"
}
let modeStr: string = "Silent";
let mode: Mode;
mode = Mode[modeStr]; // Silent
mode = Mode.Normal; // Normal
//mode = "Deleted"; // Error
mode = Mode["unknown"]; // undefined
回答by forivall
If you're ok with using Proxies, I made a more generic & compact version:
如果您可以使用代理，我制作了一个更通用和紧凑的版本：
stringEnum.ts
字符串枚举.ts
export type StringEnum<T extends string> = {[K in T]: K}
const proxy = new Proxy({}, {
get(target, property) {
return property;
}
})
export default function stringEnum<T extends string>(): StringEnum<T> {
return proxy as StringEnum<T>;
}
Usage:
用法：
import stringEnum from './stringEnum';
type Mode = "Silent" | "Normal" | "Deleted";
const Mode = stringEnum<Mode>();
回答by PhiLho
The cleanest way I found so far is to make a secondary map:
到目前为止，我发现的最干净的方法是制作辅助地图：
let reverseMode = new Map<string, Mode>();
Object.keys(Mode).forEach((mode: Mode) => {
const modeValue: string = Mode[<any>mode];
reverseMode.set(modeValue, mode);
});
Thus you can do let mode: Mode = reverseMode.get('Silent');
这样你就可以做到 let mode: Mode = reverseMode.get('Silent');
Advantages: no need to repeat the values, provides a way to enumerate the enum, keeps TSLint happy...
优点：不需要重复值，提供了枚举枚举的方法，让TSLint开心...
Edit: I originally write Mode[mode]but then TS might throw the error TS7015 on this line, so I added the cast.
编辑：我最初写Mode[mode]但后来 TS 可能会在这一行上抛出错误 TS7015，所以我添加了演员表。
