扩展抽象类定义的类属性的类型

Question

请考虑下面的例子

export abstract class Definition {
    [x: string]: string;
}

class A {
    propA = 'A';
    propB = 'B';
}

type AClassKey = keyof A;
const keyOfAClass: AClassKey = 'thisIsNotValidKey';

class B extends Definition {
    propA = 'A';
    propB = 'B';
}

type BClassKey = keyof B;

//This accepts any key because B extends Definition. How to make this accept only defined keys of B class (propA, propB)?
const keyOfBClass: BClassKey = 'thisIsValidKey';

// However if I map at least I get suggestion for defined keys (propA, propB)
type BClassMap =  {[K in keyof B]: unknown}
const bMap:BClassMap = {propA: 'suggestedByAutoComplete', propB: 'suggestedByAutoComplete', someOther: 'notSuggestedButValid'};

示例链接

是否可以使

type BClassKey

在扩展

class B

类时仅接受

abstract Definition

中定义的属性？

Answer 1

要将 keyof 限制为仅 B 的已定义属性，您可以引入一个显式声明这些属性的接口。然后，B将实现这个接口，确保在使用keyof时只考虑接口中的属性。

export abstract class Definition {
    [x: string]: string;
}

interface IB {
    propA: string;
    propB: string;
}

class B extends Definition implements IB {
    propA = 'A';
    propB = 'B';
}

// Now keyof IB only refers to explicitly defined properties of B (propA, propB)
type BClassKey = keyof IB;

const keyOfBClass: BClassKey = 'propA'; // Valid
const invalidKeyOfBClass: BClassKey = 'thisIsNotValidKey'; // Error: Type '"thisIsNotValidKey"' is not assignable to type 'keyof IB'

此外，代码干净且可读，不需要复杂的 TypeScript 实用程序类型或排除。