以下代码可用于在TypeScript中创建enum:
enum e {
hello = 1,
world = 2
};
这些值可以通过以下方式访问:
e.hello;
e.world;
我如何创建一个字符串值enum ?
enum e {
hello = "hello", // error: cannot convert string to e
world = "world" // error
};
以下代码可用于在TypeScript中创建enum:
enum e {
hello = 1,
world = 2
};
这些值可以通过以下方式访问:
e.hello;
e.world;
我如何创建一个字符串值enum ?
enum e {
hello = "hello", // error: cannot convert string to e
world = "world" // error
};
当前回答
这里有一个相当干净的解决方案,它允许继承,使用TypeScript 2.0。我没有在早期的版本上尝试过。
附加条件:该值可以是任何类型!
export class Enum<T> {
public constructor(public readonly value: T) {}
public toString() {
return this.value.toString();
}
}
export class PrimaryColor extends Enum<string> {
public static readonly Red = new Enum('#FF0000');
public static readonly Green = new Enum('#00FF00');
public static readonly Blue = new Enum('#0000FF');
}
export class Color extends PrimaryColor {
public static readonly White = new Enum('#FFFFFF');
public static readonly Black = new Enum('#000000');
}
// Usage:
console.log(PrimaryColor.Red);
// Output: Enum { value: '#FF0000' }
console.log(Color.Red); // inherited!
// Output: Enum { value: '#FF0000' }
console.log(Color.Red.value); // we have to call .value to get the value.
// Output: #FF0000
console.log(Color.Red.toString()); // toString() works too.
// Output: #FF0000
class Thing {
color: Color;
}
let thing: Thing = {
color: Color.Red,
};
switch (thing.color) {
case Color.Red: // ...
case Color.White: // ...
}
其他回答
你可以在最新的TypeScript中使用字符串枚举:
enum e
{
hello = <any>"hello",
world = <any>"world"
};
来源:https://blog.rsuter.com/how-to-implement-an-enum-with-string-values-in-typescript/
更新- 2016
最近我在React中使用的一种更健壮的方法是这样的:
export class Messages
{
static CouldNotValidateRequest: string = 'There was an error validating the request';
static PasswordMustNotBeBlank: string = 'Password must not be blank';
}
import {Messages as msg} from '../core/messages';
console.log(msg.PasswordMustNotBeBlank);
这对我来说很管用:
class MyClass {
static MyEnum: { Value1; Value2; Value3; }
= {
Value1: "Value1",
Value2: "Value2",
Value3: "Value3"
};
}
or
module MyModule {
export var MyEnum: { Value1; Value2; Value3; }
= {
Value1: "Value1",
Value2: "Value2",
Value3: "Value3"
};
}
8)
更新:在发布这篇文章后不久,我发现了另一种方法,但忘记发布更新(然而,上面已经有人提到过了):
enum MyEnum {
value1 = <any>"value1 ",
value2 = <any>"value2 ",
value3 = <any>"value3 "
}
为什么不直接使用本地方式访问枚举的字符串呢?
enum e {
WHY,
NOT,
USE,
NATIVE
}
e[e.WHY] // this returns string 'WHY'
我认为你应该试试这个,在这种情况下,变量的值不会改变,它的工作方式很像枚举,使用类也可以,唯一的缺点是你可以错误地改变静态变量的值这是我们不希望在枚举中发生的。
namespace portal {
export namespace storageNames {
export const appRegistration = 'appRegistration';
export const accessToken = 'access_token';
}
}
我也有同样的问题,然后想出了一个很好用的函数:
每个条目的键和值都是字符串,并且相同。 每个条目的值都是从键派生出来的。(即。“不要重复你自己”,不像字符串值的常规枚举) TypeScript类型成熟且正确。(防止拼写错误) 还有一种简单的方法可以让TS自动完成您的选项。(如。打字MyEnum。,并立即看到可用的选项) 还有其他一些优点。(见答案底部)
效用函数:
export function createStringEnum<T extends {[key: string]: 1}>(keysObj: T) {
const optionsObj = {} as {
[K in keyof T]: keyof T
// alternative; gives narrower type for MyEnum.XXX
//[K in keyof T]: K
};
const keys = Object.keys(keysObj) as Array<keyof T>;
const values = keys; // could also check for string value-overrides on keysObj
for (const key of keys) {
optionsObj[key] = key;
}
return [optionsObj, values] as const;
}
用法:
// if the "Fruit_values" var isn't useful to you, just omit it
export const [Fruit, Fruit_values] = createStringEnum({
apple: 1,
pear: 1,
});
export type Fruit = keyof typeof Fruit; // "apple" | "pear"
//export type Fruit = typeof Fruit_values[number]; // alternative
// correct usage (with correct types)
let fruit1 = Fruit.apple; // fruit1 == "apple"
fruit1 = Fruit.pear; // assigning a new fruit also works
let fruit2 = Fruit_values[0]; // fruit2 == "apple"
// incorrect usage (should error)
let fruit3 = Fruit.tire; // errors
let fruit4: Fruit = "mirror"; // errors
现在有人可能会问,这个“基于字符串的enum”比只使用:
type Fruit = "apple" | "pear";
有几个优点:
Auto-complete is a bit nicer (imo). For example, if you type let fruit = Fruit., Typescript will immediately list the exact set of options available. With string literals, you need to define your type explicitly, eg. let fruit: Fruit = , and then press ctrl+space afterward. (and even that results in unrelated autocomplete options being shown below the valid ones) The TSDoc metadata/description for an option is carried over to the MyEnum.XXX fields! This is useful for providing additional information about the different options. For example: You can access the list of options at runtime (eg. Fruit_values, or manually with Object.values(Fruit)). With the type Fruit = ... approach, there is no built-in way to do this, which cuts off a number of use-cases. (for example, I use the runtime values for constructing json-schemas)