英文:
Interface key as value instead of type
问题
export interface 动作 {
启动: "start",
停止: "stop"
}
// 从库中导入动作后，需要进行如下的相等性检查：
import { 动作 } from '我的库';
// 在某个逻辑中，x 是字符串类型，但本质上是动作中的一种
if (x === 动作.启动) { }
英文:
A third-party library exposes different actions as part of an interface as given below:
export interface actions {
start: "start",
stop: "stop"
}
After importing actions from this library, there's an equality check to be done as given below:
import { actions } from 'my-library';
// as part of some logic where x is of string type but is essentially one of the actions
if (x === actions.start) { }
The above code throws the following error:
'actions' only refers to a type, but is being used as a value here.
How can we use actions interface like an enum?
答案1
得分: 1
以下是翻译好的部分：
"你不能在运行时使用一个类型，不管它来自哪里。所以如果这是来自一个你无法控制的依赖项，那么你无法做太多事情。
如果库没有导出要使用的值，那么你不应该将其用作值。
你可能应该做类似这样的事情：
export interface actions {
start: "start",
stop: "stop"
}
const x: keyof actions = 'start'
if (x === 'start') console.log('start')
这里你确实获得了枚举的行为，因为TypeScript会在你使用不是 action 的东西时发出警告。
if (x === 'bad') console.log('bad')
// 这个比较似乎是不打算的，因为类型 ' "start" ' 和 ' "bad" ' 没有重叠。(2367)
不了解该库的具体情况，很难提供更好的建议。"
英文:
You cannot use a type at runtime, no matter where it comes from. So if this is coming from a dependency you don't control, then there isn't much you can do.
If the library does not export a value to use, then you aren't meant to use it as a value.
You are probably meant to do something like:
export interface actions {
start: "start",
stop: "stop"
}
const x: keyof actions = 'start'
if (x === 'start') console.log('start')
And you do get enum like behavior here because typescript will complain if you use something that isn't an action.
if (x === 'bad') console.log('bad')
// This comparison appears to be unintentional because the types '"start"' and '"bad"'
// have no overlap.(2367)
Without knowing the specifics of that library, it's hard to give better advice.
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