如何声明一个在 Typescript 中引发错误的函数
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How to declare a function that throws an error in Typescript
提问by The224
In Java I would declare a function like this:
在 Java 中，我会声明一个这样的函数：
public boolean Test(boolean test) throws Exception {
if (test == true)
return false;
throw new Exception();
}
And I can use this function without handling the exception.
而且我可以在不处理异常的情况下使用这个函数。
If it is possible, how to do the same in Typescript? The compiler will tell me that I can't use the function without a try/catch.
如果可能，如何在 Typescript 中做同样的事情？编译器会告诉我，如果没有 try/catch，我将无法使用该函数。
回答by Estus Flask
There is no such feature in TypeScript. It's possible to specify error type only if a function returns an error, not throws it (this rarely happens and is prone to be antipattern).
TypeScript 中没有这样的功能。仅当函数返回错误而不是抛出错误时才可以指定错误类型（这种情况很少发生并且容易成为反模式）。
The only relevant type is never. It is applicable only if a function definitely throws an error, it cannot be more specific than that. It's a type as any other, it won't cause type error as long as it doesn't cause type problems:
唯一相关的类型是never. 仅当一个函数肯定会抛出错误时才适用，它不能比这更具体。它和其他类型一样，只要不引起类型问题，就不会引起类型错误：
function Test(): never => {
throw new Error();
}
Test(); // won't cause type error
let test: boolean = Test(); // will cause type error
When there is a possibility for a function to return a value, neveris absorbed by return type.
当函数有可能返回一个值时，never被返回类型吸收。
It's possible to specify it in function signature, but for reference only:
可以在函数签名中指定它，但仅供参考：
function Test(test: boolean): boolean | never {
if (test === true)
return false;
throw new Error();
}
It can give a hint to a developer that unhandled error is possible (in case when this is unclear from function body), but this doesn't affect type checks and cannot force try..catch; the type of this function is considered (test: boolean) => booleanby typing system.
它可以提示开发人员可能出现未处理的错误（以防函数体不清楚），但这不会影响类型检查，也不能强制try..catch；该函数的类型(test: boolean) => boolean由类型系统考虑。
回答by sompnd
It is not possible at this moment. You can check out this requested feature: https://github.com/microsoft/TypeScript/issues/13219
目前是不可能的。您可以查看此请求的功能：https: //github.com/microsoft/TypeScript/issues/13219
回答by Flavien Volken
You cannot using pure ts (v<3.9) I hope it will be available in the future. A workaround is however possible, it consists of hiding the possible thrown types in the method's signature to then recover those types in the catch block. I made a package with this workaround here: https://www.npmjs.com/package/ts-throwable/v/latest
您不能使用纯 ts (v<3.9) 我希望将来可以使用它。然而，一种解决方法是可能的，它包括在方法的签名中隐藏可能抛出的类型，然后在 catch 块中恢复这些类型。我在这里用这个解决方法做了一个包：https: //www.npmjs.com/package/ts-throwable/v/latest
usage is more or less as follow:
用法或多或少如下：
import { throwable, getTypedError } from 'ts-throwable';
class CustomError extends Error { /*...*/ }
function brokenMethod(): number & throwable<CustomError> {
return Math.random() < 0.5 ? 42 : throw new CustomError("Boom!");
}
try {
const answer: number = brokenMethod()
}
catch(error){
// `typedError` is now an alias of `error` and typed as `CustomError`
const typedError = getTypedError(error, brokenMethod);
}
