如何解決錯誤？ 打字稿：類型'ErrorRequestHandler'不能分配給類型'IMiddleware'

Question

在以下代碼中，我遇到了類型重新分配錯誤：

export default class AbstractController extends Middleware {

    get middleware(): Express.RequestHandler | Express.ErrorRequestHandler { // (6,22)
        //...
    }

}

錯誤文字：

src/controller/AbstractController.ts(6,22): error TS2415: Class 'AbstractController' incorrectly extends base class 'Middleware'.
  Types of property 'middleware' are incompatible.
    Type 'ErrorRequestHandler | RequestHandler' is not assignable to type 'IMiddleware'.
      Type 'ErrorRequestHandler' is not assignable to type 'IMiddleware'.

聲明RequestHandler和ErrorRequestHandler接口：

interface RequestHandler {
    (req: Request, res: Response, next: NextFunction): any;
}

interface ErrorRequestHandler {
    (err: any, req: Request, res: Response, next: NextFunction): any;
}

聲明中間件類：

export interface IMiddleware {
    (req: http.IncomingMessage, res: http.ServerResponse): void;
}

export default class Middleware {

    get middleware(): IMiddleware {
        throw new Error('Не определен middleware.');
    }

}

我不需要了解如何解決它，而是要了解導致錯誤的原因。

Answer 1

Middleware類期望將IMiddleware作為middleware()返回類型。

您的界面應擴展IMiddleware！

interface RequestHandler extends IMiddleware {
    (req: Request, res: Response, next: NextFunction): any;
}

interface ErrorRequestHandler extends IMiddleware {
    (err: any, req: Request, res: Response, next: NextFunction): any;
}

但是， ErrorRequestHandler的簽名與IMiddleware不匹配

也許您應該創建第二個接口來表示它。