Node.js 无法读取属性'；保存'；未定义角的

在Node.js中写入的服务器返回以下错误消息：

TypeError: Cannot read property 'save' of undefined
    at e:\_Angular5\administration\routes\product.js:34:12
    at e:\_Angular5\administration\node_modules\mongoose\lib\model.js:3930:16
    at (anonymous function).call (e:\_Angular5\administration\node_modules\mongoose\lib\query.js:3018:9)
    at model.Query.Query._findOne (e:\_Angular5\administration\node_modules\mongoose\lib\query.js:1497:12)
    at model.Query.Query.findOne (e:\_Angular5\administration\node_modules\mongoose\lib\query.js:1611:8)

我的服务器代码server.js：

const express = require('express');

const bodyParser = require('body-parser');
const path = require('path');
const http = require('http');
const app  = express();

var user = require('./routes/user.js');
var product = require('./routes/product.js');
const api = require('./server/api');

app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false}));

app.use(function(req, res, next) {
  res.setHeader("Access-Control-Allow-Origin", "*");
  res.setHeader('Access-Control-Allow-Methods', 'PUT, GET, POST, DELETE, OPTIONS');
  res.setHeader("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept, Authorization, Access-Control-Allow-Credentials");
  res.setHeader("Access-Control-Allow-Credentials", "true");
  next();
});

app.use(express.static(path.join(__dirname, 'dist')));

app.post('/register', user.signup);
app.post('/login', user.login); 
app.get('/user/:id', user.getuserDetails);

app.put('/user/:id', user.updateUser);
app.post('/user/products/:id', product.saveproduct);  // did not work

app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname, 'dist/index.html'));
});



const port = process.env.PORT || '4200';
app.set('port', port);

const server = http.createServer(app);

server.listen(port, () => console.log(`Running on localhost:${port}`));

routes/product.js:

var mongoose = require( 'mongoose' );
var Product = require('../models/products');
var config = require('../server/config');

exports.saveproduct = function(req, res, next){

    const userid = req.params.id;
    const product_name = req.body.product_name;   
    const product_type = req.body.product_type;
    const product_desc = req.body.product_desc;
    const expid = req.body.expid;

    if (!userid || !product_name || !product_type || !product_desc) {
        return res.status(422).send({ success: false, message: 'Posted data is not correct or incompleted.' });
    } else {

    if (userid) {   
        Product.findById({product_name: req.body.product_name} ).exec(function(err, product){

            if(err){ res.status(400).json({ success: false, message: 'Error processing request '+ err }); }

            if(product) {
                product.product_name = product_name;
                product.product_type = product_type;
                product.product_desc = product_desc;
      }     
            product.save(function(err) { 

                if(err){ res.status(400).json({ success: false, message: 'Error processing request '+ err }); }
                res.status(201).json({
                    success: true,
                    message: 'product updated successfully'
                });
            });
        });

    }else{
        let oProduct = new Product({
            userid: uid,
            product_name: product_name,
            product_type: product_type,
            product_desc: product_desc

        });

        oProduct.save(function(err) { // error 
            if(err){ res.status(400).json({ success: false, message: 'Error processing request '+ err }); }

            res.status(201).json({
                success: true,
                message: 'Product saved successfully'
            });
        });

    }
    }
}

src/app/product/user-products.component.ts

    @Component({
      selector: 'app-user-products',
      templateUrl: './user-products.component.html',
      styleUrls: ['./user-products.component.css']
    })
    export class UserProductsComponent implements OnInit {

      user: User;
      UserType = UserType;

      product_name: string;
      product_type: ProductType;
      ProductType = ProductType;
      product_desc: string;

      produktForm: FormGroup;
      products: Product;
      userObj: any;

      productid: string;
      constructor(private fb: FormBuilder,
        private route: ActivatedRoute,
        private router: Router,
        private productsService: ProductsService,
        private authService: AuthService) { }


      ngOnInit() {
        this.userObj = this.authService.currentUser;

        this.route.params.subscribe((params: any) => {
          if (params.id) {
            console.log('params.id : ');
            console.log(params.id);
            this.productid = params['_id'];
            console.log('this.productid : ');
            console.log(this.productid);
          }
        });

        this.produktForm = this.fb.group({
          product_name: ['', Validators.required],
          product_type: ['', Validators.required],
          product_desc: ['', Validators.required]
        });

      }


      saveProduct(produktForm: any) {

        if (this.produktForm.dirty && this.produktForm.valid) {
          const theForm = this.produktForm.value;
          if (this.productid !== '') {
            produktForm.productid = this.productid;
          }

          this.productsService.add_product(this.userObj.userid, theForm)
            .subscribe(data => {
              if (data.success === false) {
                if (data.errcode) {
                  this.authService.logout();
                  this.router.navigate(['login']);
                }
                console.log('Error ' + data.message);

              } else {
                console.log('Success ' + data.message);

              }
              // if (!this.productid) {
              this.produktForm.reset();
              // }
            });
        }
      }
    }

我不知道为什么save方法不起作用。如何纠正错误？ 从表格中发送的数据如下：

{产品名称：产品类型：产品名称：产品名称：产品ID:未定义}

 if (err) {
     res.status(400).json({
         success: false,
         message: 'Error processing request ' + err
     });
 }

 if (product) {
     product.product_name = product_name;
     product.product_type = product_type;
     product.product_desc = product_desc;
 }
 product.save(function(err) {

     if (err) {
         res.status(400).json({
             success: false,
             message: 'Error processing request ' + err
         });
     }
     res.status(201).json({
         success: true,
         message: 'product updated successfully'
     });
 });

您得到的

错误是因为您的产品对象
未定义
。您正在检查
对象是否存在并分配属性，但在尝试调用
product.save（）
时，您没有检查对象是否存在

尝试将
product.save（）
嵌套在
的内部，如果（product）{}
有效，则解决方案如下：

var mongoose = require( 'mongoose' );
var Product = require('../models/products');
var config = require('../server/config');

exports.saveproduct = function(req, res, next){


    const userid = req.params.id;
    const product_name = req.body.product_name;  
    const product_type = req.body.product_type;
    const product_desc = req.body.product_desc;
    const expid = req.body.expid;

    if (!userid || !product_name || !product_type || !product_desc) {
        return res.status(422).send({ success: false, message: 'Posted data is not correct or incompleted.' });
    } else {

    if (expid) {        
        Product.findById({product_name: req.body.product_name} ).exec(function(err, product){
            if(err){
        res.status(400).json({ success: false, message: 'Error processing request '+ err });
      }
            if(product) {
                product.product_name = product_name;
                product.product_type = product_type;
                product.product_desc = product_desc;
      }
            product.save(function(err) {
                if(err){ res.status(400).json({ success: false, message: 'Error processing request '+ err }); }
                res.status(201).json({
                    success: true,
                    message: 'product updated successfully'
                });
            });
        });

    }else{

        let oProduct = new Product({
            userid: userid,
            product_name: product_name,
            product_type: product_type,
            product_desc: product_desc
        });
        oProduct.save(function(err) {
            if(err){ res.status(400).json({ success: false, message: 'Error processing request '+ err }); }

            res.status(201).json({
                success: true,
                message: 'Product saved successfully'
            });
        });
    console.log( 'Product saved successfully');
    }
    }
}

在某个时刻，您检查
如果（产品）{do some stuff}
，然后立即（其中
产品
可能未定义）调用
产品.save（）
，因此。。。有道理。