我正在尝试为我的node.js应用程序在typescript中实现一个基类。我们的想法是所有实体/对象都可以扩展基类以用于它们的CRUD。
这是基类：
export class Base {
Model: any;
constructor(modelName: object) {
this.Model = modelName;
}
public getAll(req: Request, res: Response) {
console.log(this.Model);
this.Model.find({}, (err: Error, result: any) => {
if (err) {
res
.status(HttpStatus.NOT_FOUND)
.send({
message: HttpStatus.getStatusText(HttpStatus.NOT_FOUND),
error: err
});
}
res
.status(HttpStatus.OK)
.send({
message: HttpStatus.getStatusText(HttpStatus.OK),
output: result
});
});
}
public get(params: object, res: Response) {
this.Model.find(params, (err: Error, result: any) => {
if (err) {
res
.status(HttpStatus.NOT_FOUND)
.send({
message: HttpStatus.getStatusText(HttpStatus.NOT_FOUND),
error: err
});
}
res
.status(HttpStatus.OK)
.send({
message: HttpStatus.getStatusText(HttpStatus.OK),
output: result
});
});
}
public create(params: object, res: Response) {
console.log(this.Model);
this.Model.create(params, (err: Error, result: any) => {
if (err) {
res
.status(HttpStatus.INTERNAL_SERVER_ERROR)
.send({
message: HttpStatus.getStatusText(HttpStatus.INTERNAL_SERVER_ERROR),
error: err
});
}
res
.status(HttpStatus.CREATED)
.send({
message: HttpStatus.getStatusText(HttpStatus.CREATED),
output: result
});
});
}
public update(params: object, res: Response) {
this.Model.update(params, (err: Error, result: any) => {
if (err) {
res
.status(HttpStatus.INTERNAL_SERVER_ERROR)
.send({
message: HttpStatus.getStatusText(HttpStatus.INTERNAL_SERVER_ERROR),
error: err
});
}
res
.status(HttpStatus.OK)
.send({
message: HttpStatus.getStatusText(HttpStatus.OK),
output: result
});
});
}
public delete(params: object, res: Response) {
this.Model.delete(params, (err: Error, result: any) => {
if (err) {
res
.status(HttpStatus.NOT_FOUND)
.send({
message: HttpStatus.getStatusText(HttpStatus.NOT_FOUND),
error: err
});
}
res
.status(HttpStatus.OK)
.send({
message: HttpStatus.getStatusText(HttpStatus.OK),
output: result
});
});
}
public search(req: Request, res: Response) {
}
public filter(req: Request, res: Response) {
}
}
子课程如下：
class AssetClass extends Base {
constructor(model: object) {
model = AssetClassModel;
logger.debug("creating the assetClass constructor");
super(model);
}
public get(req: Request, res: Response) {
const params: object = {
name: req.body.name
};
super.get(params, res);
}
public create(req: Request, res: Response) {
logger.debug("creating the asset class");
const params: object = {
name: req.body.name,
manufacturer: req.body.manufacturer,
category: req.body.category
};
super.create(params, res);
}
public update(req: Request, res: Response) {
const params: object = {
name: req.body.name,
manufacturer: req.body.manufacturer,
category: req.body.category
};
super.update(params, res);
}
public delete(req: Request, res: Response) {
const params: object = {
name: req.body.name,
};
super.delete(params, res);
}
}
export const assetClass: AssetClass = new AssetClass(AssetClassModel);
我在app.ts
中定义了两个路径，create和getAllapp.post("/test", assetClass.create);
app.get("/test", assetClass.get);
当我测试我的应用程序时，出现以下错误：
[Node] TypeError: Cannot read property 'Model' of undefined
[Node] at create (/home/hassaan/apollo-be/rest/dist/controllers/base.controller.js:49:26)
[Node] at create (/home/hassaan/apollo-be/rest/dist/controllers/assetClass.controller.js:28:15)
[Node] at Layer.handle [as handle_request] (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/layer.js:95:5)
[Node] at next (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/route.js:137:13)
[Node] at Route.dispatch (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/route.js:112:3)
[Node] at Layer.handle [as handle_request] (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/layer.js:95:5)
[Node] at /home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:281:22
[Node] at Function.process_params (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:335:12)
[Node] at next (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:275:10)
[Node] at serveStatic (/home/hassaan/apollo-be/rest/node_modules/serve-static/index.js:75:16)
[Node] at Layer.handle [as handle_request] (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/layer.js:95:5)
[Node] at trim_prefix (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:317:13)
[Node] at /home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:284:7
[Node] at Function.process_params (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:335:12)
[Node] at next (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:275:10)
[Node] at app.use (/home/hassaan/apollo-be/rest/dist/app.js:86:5)
[Node] at Layer.handle [as handle_request] (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/layer.js:95:5)
[Node] at trim_prefix (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:317:13)
[Node] at /home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:284:7
[Node] at Function.process_params (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:335:12)
[Node] at next (/home/hassaan/apollo-be/rest/node_modules/express/lib/router/index.js:275:10)
[Node] at app.use (/home/hassaan/apollo-be/rest/dist/app.js:71:5)
从我从这个错误中收集的内容中，通过assetClass类的未实例化对象调用基类中的this.Model，即未定义模型
但是如果我在app.ts文件中调用asset.log资产块对象，我可以看到它是一个有效的定义实例。
我做错了什么？
答案 0 :(得分：2)
在javacript中，this是由调用者决定的，当你向某人传递一个函数时，你只传递函数而没有来自它的实例的内存。这就是路由引擎调用this时undefined为create的原因。要bind函数的实例，您需要使用bind函数或使用箭头函数：
app.post("/test", assetClass.create.bind(assetClass));
app.get("/test", assetClass.get.bind(assetClass));
// Or
app.post("/test", (req, res) => assetClass.create(req, res));
app.get("/test", (req, res) => assetClass.get(req, res));