如何在TypeScript中注入枚举？

Question

How to inject Enums in TypeScript? Is this possible and recommended?

enums.ts:

export enum Environment {
    Development = 'Development',
    Production = 'Production',
    Test = 'Test'
}

file:

import { Environment as _Environment } from '../enums';
function myfunc(Environment: Environment = _Environment): void {}

I get:

application/libs/config/index.ts:23:18 - error TS2749: 'Environment' refers to a value, but is being used as a type here.

23     Environment: Environment = _Environment

Answer 1

This works fine

function myfunc(Environment: _Environment): void {}

However, if you want to utilize default parameters you can try something like this

function myfunc(Environment: _Environment = _Environment.Development): void {}

Answer 2

Enum is kind of union/variant type. It means that it defines group of possible values, but is not a value itself. Your function has an argument of type Environment , and it means that you can assign one of possible value existing in the enum Enviroment , but not Enum itself as you try to do, as Enviroment itself is not a value but a type.

function myfunc(Environment: Environment = _Environment.Production ): void {}

As you can see I am choosing arbitrarily one from possible values in the Enum.

You can look on Enums like on unions with static structural representation . It means that:

type T = 'a' | 'b';
enum TEnum {
  a = 'a'
  b = 'b'
}

// using
const a: T = 'a' // direct setting the value
const b: TEnum = TEnum.b // using existing enum structure to set the value

Answer 3

This is how you would do it. Default envoronment being Development.

export enum Environment {
    Development = 'Development',
    Production = 'Production',
    Test = 'Test'
}

function myfunc(e: Environment = Environment.Development): void {}