Question

我正在围绕Express JS创建一个抽象层，但是遇到了问题。考虑以下代码（请参阅底部），在调用registerRoute并单击该行时：

expressFnc(route, (req: any, res: any, next: any) => dummy(req, res, next));

我遇到错误：

无法读取未定义的属性“ lazyrouter”

在这种情况下，我认为“ this”适用于ExpressJS（lib / application.js：479：10）。

const express = require("express");

export class ExpressHttpHost implements IHttpHost {
  private host: any = express();
  private contentResolver?: ContentResolver;

  public configure(contentResolver: ContentResolver): void {
    this.contentResolver = contentResolver;
  }

  public registerRoute(
    route: string,
    verb: HttpVerb,
    handler: (request: HttpRequest) => HttpResponse,
  ): void {
    switch (verb) {
      case HttpVerb.Get:
        this.createDummyRequest(this.host.get, route, handler);
        break;
      case HttpVerb.Delete:
        this.createDummyRequest(this.host.delete, route, handler);
        break;
      case HttpVerb.Options:
        this.createDummyRequest(this.host.options, route, handler);
        break;
      case HttpVerb.Patch:
        this.createDummyRequest(this.host.patch, route, handler);
        break;
      case HttpVerb.Post:
        this.createDummyRequest(this.host.post, route, handler);
        break;
      case HttpVerb.Put:
        this.createDummyRequest(this.host.put, route, handler);
        break;
      case HttpVerb.All:
        this.createDummyRequest(this.host.get, route, handler);
        this.createDummyRequest(this.host.delete, route, handler);
        this.createDummyRequest(this.host.options, route, handler);
        this.createDummyRequest(this.host.patch, route, handler);
        this.createDummyRequest(this.host.post, route, handler);
        this.createDummyRequest(this.host.put, route, handler);
        break;
      default:
        throw new Error("Verb is not supported.");
    }
  }

  public start(options: IHttpHostOptions): void {
    this.host.listen(options.port ? options.port : 80);
  }

  private createHttpRequest(expressReq: any): HttpRequest {
    return new HttpRequest(
      expressReq.headers,
      expressReq.params,
      expressReq.body,
    );
  }

  private createDummyRequest(expressFnc: any, route: string, handler: (request: HttpRequest) => HttpResponse): void {
    const dummy = (expressReq: any, expressRes: any, next: any) => {
      const httpRequest = this.createHttpRequest(expressReq);

      const response = handler(httpRequest);
      const responseStatus = response.status();
      const responseMimeType = response.mimeType();
      const responseContent = response.content(this.contentResolver);

      expressRes.set("Content-Type", responseMimeType);
      expressRes.status(responseStatus);
      expressRes.send(responseContent);
      next();
    };
    expressFnc(route, (req: any, res: any, next: any) => dummy(req, res, next));
  }
}

Answer 1

之所以会发生这种情况，是因为在将Express函数作为参数传递时会松散引用宿主对象。尝试手动将它们绑定回去。请参阅下面的开关中的绑定：

const express = require("express");

export class ExpressHttpHost implements IHttpHost {
  private host: any = express();
  private contentResolver?: ContentResolver;

  public configure(contentResolver: ContentResolver): void {
    this.contentResolver = contentResolver;
  }

  public registerRoute(
    route: string,
    verb: HttpVerb,
    handler: (request: HttpRequest) => HttpResponse,
  ): void {
    switch (verb) {
      case HttpVerb.Get:
        this.createDummyRequest(this.host.get.bind(this.host), route, handler);
        break;
      case HttpVerb.Delete:
        this.createDummyRequest(this.host.delete.bind(this.host), route, handler);
        break;
      case HttpVerb.Options:
        this.createDummyRequest(this.host.options.bind(this.host), route, handler);
        break;
      case HttpVerb.Patch:
        this.createDummyRequest(this.host.patch.bind(this.host), route, handler);
        break;
      case HttpVerb.Post:
        this.createDummyRequest(this.host.post.bind(this.host), route, handler);
        break;
      case HttpVerb.Put:
        this.createDummyRequest(this.host.put.bind(this.host), route, handler);
        break;
      case HttpVerb.All:
        this.createDummyRequest(this.host.get.bind(this.host), route, handler);
        this.createDummyRequest(this.host.delete.bind(this.host), route, handler);
        this.createDummyRequest(this.host.options.bind(this.host), route, handler);
        this.createDummyRequest(this.host.patch.bind(this.host), route, handler);
        this.createDummyRequest(this.host.post.bind(this.host), route, handler);
        this.createDummyRequest(this.host.put.bind(this.host), route, handler);
        break;
      default:
        throw new Error("Verb is not supported.");
    }
  }

  public start(options: IHttpHostOptions): void {
    this.host.listen(options.port ? options.port : 80);
  }

  private createHttpRequest(expressReq: any): HttpRequest {
    return new HttpRequest(
      expressReq.headers,
      expressReq.params,
      expressReq.body,
    );
  }

  private createDummyRequest(expressFnc: any, route: string, handler: (request: HttpRequest) => HttpResponse): void {
    const dummy = (expressReq: any, expressRes: any, next: any) => {
      const httpRequest = this.createHttpRequest(expressReq);

      const response = handler(httpRequest);
      const responseStatus = response.status();
      const responseMimeType = response.mimeType();
      const responseContent = response.content(this.contentResolver);

      expressRes.set("Content-Type", responseMimeType);
      expressRes.status(responseStatus);
      expressRes.send(responseContent);
      next();
    };
    expressFnc(route, (req: any, res: any, next: any) => dummy(req, res, next));
  }
}

Answer 2

这个问题发生在我身上，我花了几个小时和额外的支持来解决。我的建议是好好阅读编译错误，因为它应该告诉你错误是在你的代码库中的哪个地方引起的。

就我而言，这是由

server.post(`/url/path/to/page`, myMiddleware(), MyClass.myNonExistentFunction);

在复杂的合并期间，对一个不存在的函数的引用已经悄悄进入我的代码库。

这个编译错误的部分问题是它没有命名未定义的回调——在这种情况下是“MyClass.myNonExistentFunction”。

Express JS：无法读取未定义的属性“ lazyrouter”

2 个答案: