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
Typescript中的字符串枚举:
字符串枚举是一个类似的概念,但是有一些细微的运行时差异,如下文所述。在string enum中,每个成员必须用string字面值或另一个string enum成员常量初始化。
enum Direction {
Up = "UP",
Down = "DOWN",
Left = "LEFT",
Right = "RIGHT",
}
虽然字符串枚举没有自动递增的行为,但字符串枚举的好处是它们很好地“序列化”。换句话说,如果你正在调试并且必须读取一个数值enum的运行时值,这个值通常是不透明的——它本身没有传达任何有用的含义(尽管反向映射通常会有所帮助),字符串enum允许你在代码运行时给出一个有意义且可读的值,与枚举成员本身的名称无关。 参考链接如下。
在这里输入链接描述
其他回答
在TypeScript 0.9.0.1中,尽管会出现编译器错误,但编译器仍然可以将ts文件编译为js文件。代码工作如我们所料,Visual Studio 2012可以支持自动代码补全。
更新:
在语法上,TypeScript不允许我们用字符串值创建enum,但我们可以破解编译器:p
enum Link
{
LEARN = <any>'/Tutorial',
PLAY = <any>'/Playground',
GET_IT = <any>'/#Download',
RUN_IT = <any>'/Samples',
JOIN_IN = <any>'/#Community'
}
alert('Link.LEARN: ' + Link.LEARN);
alert('Link.PLAY: ' + Link.PLAY);
alert('Link.GET_IT: ' + Link.GET_IT);
alert('Link[\'/Samples\']: Link.' + Link['/Samples']);
alert('Link[\'/#Community\'] Link.' + Link['/#Community']);
操场上
一个俗套的说法是:-
CallStatus.ts
enum Status
{
PENDING_SCHEDULING,
SCHEDULED,
CANCELLED,
COMPLETED,
IN_PROGRESS,
FAILED,
POSTPONED
}
export = Status
Utils.ts
static getEnumString(enum:any, key:any):string
{
return enum[enum[key]];
}
如何使用
Utils.getEnumString(Status, Status.COMPLETED); // = "COMPLETED"
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)
我正在寻找一种方法来实现typescript枚举中的描述(v2.5),这种模式适合我:
export enum PriceTypes {
Undefined = 0,
UndefinedDescription = 'Undefined' as any,
UserEntered = 1,
UserEnteredDescription = 'User Entered' as any,
GeneratedFromTrade = 2,
GeneratedFromTradeDescription = 'Generated From Trade' as any,
GeneratedFromFreeze = 3,
GeneratedFromFreezeDescription = 'Generated Rom Freeze' as any
}
...
GetDescription(e: any, id: number): string {
return e[e[id].toString() + "Description"];
}
getPriceTypeDescription(price: IPricePoint): string {
return this.GetDescription(PriceTypes, price.priceType);
}
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: // ...
}