Question

当我沿着路线：“ / gallery”时，我从文件“ ./posts.json”中获取所有项目，并将它们显示在屏幕上。但是当我转向路线：'/ gallery /：id'时，我想通过其id收到一件物品。

但是我得到一个错误：const pictureId = this.formatePicture.findIndex(p => p.id == parseInt(id)); TypeError: this.formatePicture.findIndex is not a function.我尝试用for in做data，但是循环之后没有对象属性。

告诉我我做错了什么以及如何解决此问题，以便我在转到“ / gallery /：id”路线时通过id获得商品 < / p>

app.js：

const express = require('express');
const Database = require('./db');

const app = express();
const port = 3000;
const db = new Database();

app.use(express.json());

app.get('/gallery', (req, res) => {
    if (req.query.id) {
        const picture = db.read(req.query.id);
        picture.then(data => {
            res.send(data);
        })
    } else {
        const pictures = db.read();
        pictures.then(data => {
            res.send(data);
        })
    }
});

app.get('/gallery/:id', (req, res) => {
    const picture = db.read(req.params.id);
    if (!picture) {
        res.status(404);
        res.send();
    } else {
        picture.then(data => {
            res.send(data);
        })
    }
});

app.listen(port, () => {
    console.log(`Example app listening on port ${port}`)
});

db.js：

const fs = require('fs');
class Database {
constructor() {
     this.formatePicture = [];
}
    read (id) {
        return new Promise((resolve, reject) => {
            fs.readFile('./posts.json', 'utf-8', (err, data) => {
                if (err) {
                    reject(err)
                }else if(id) {
                    this.formatePicture = JSON.parse(data);
                    const pictureId = this.formatePicture.findIndex(p => p.id == parseInt(id));
                    resolve(pictureId)
                }
                else {
                    resolve(data)
                }
            })
        })
    }
}

module.exports = Database;

posts.json：

{
  "posts": [
    {
      "id": 1,
      "date": "2018-10-22T14:10:37.578Z",
      "title": "accusamus beatae ad facilis cum similique qui sunt",
      "url": "https://i.pinimg.com/originals/90/39/16/903916b9f0db6992f1a4b66ae3129fbe.jpg"
    },
    {
      "id": 2,
      "date": "2018-10-22T14:10:37.578Z",
      "title": "reprehenderit est deserunt velit ipsam",
      "url": "https://vignette.wikia.nocookie.net/okup/images/d/da/C683c20a5b0ae062b2325653f2fd3bdf.jpg/revision/latest?cb=20170131193210&path-prefix=da"
    }
      ]
}

Answer 1

解析的数据是一个对象，您需要定位的数组在字段posts

中

this.formatePicture.posts.findIndex(...)

另一种无需修改数据库代码即可实现此目的的方法是更改posts.json中的结构，使其看起来像这样

[
    {
      "id": 1,
      "date": "2018-10-22T14:10:37.578Z",
      "title": "accusamus beatae ad facilis cum similique qui sunt",
      "url": "https://i.pinimg.com/originals/90/39/16/903916b9f0db6992f1a4b66ae3129fbe.jpg"
    },
    {
      "id": 2,
      "date": "2018-10-22T14:10:37.578Z",
      "title": "reprehenderit est deserunt velit ipsam",
      "url": "https://vignette.wikia.nocookie.net/okup/images/d/da/C683c20a5b0ae062b2325653f2fd3bdf.jpg/revision/latest?cb=20170131193210&path-prefix=da"
    }
]

作为旁注：

您可能想使用find而不是findIndex，因为pictureId是包含您共享的初始代码的索引

看起来可能是这样

const picture = this.formatePicture.find(p => p.id == parseInt(id));

// checking if we found an entry first
if (picture) {
    resolve(picture.id);
} else {
    reject(/* some error about resource not being found */)
}

如何解决按ID查找商品的问题？

1 个答案:

作为旁注：