REST-API-05-Sync-Await

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修正之前的一个错误

nodemon 用于开发时，代码修改后，自动重启服务
修改 package.json, 删除 dependencies 下的 nodemon
安装为dev dependencies

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$ npm install nodemon --save-dev

package.json

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{
  "name": "APIProject",
  "version": "1.0.0",
  "description": "",
  "main": "app.js",
  "scripts": {
    "start": "nodemon app.js",
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "1623695606@qq.com",
  "license": "ISC",
  "dependencies": {
    "body-parser": "^1.17.2",
    "express": "^4.15.4",
    "mongoose": "^4.11.7",
    "morgan": "^1.8.2"
  },
  "devDependencies": {
    "nodemon": "^1.11.0"
  }
}

Sync-Await 用法

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//controllers/users.js 片段
 const User = require('../models/user')
module.exports = {
    index: async (req,res,next) => {
        //Async-Await 方式
        try {
            const users = await User.find();
            res.status(200).json(users);
        } catch (error) {
            next(error);
        }
    },
    newUser: async (req,res,next) => {
        try{
            const newUser = new User(req.body);
            const user = await newUser.save();
            res.status(200).json(user);
            console.debug('save ' ,user);
        }catch(err){
            next(err);
        }
    }
}
``` 
## 安装
express-promise-router , 可以不用写 try catch
```bash
$ npm install express-promise-router

修改 routers/users.js , 配置使用 express-promise-router

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const express = require('express');
//const router = express.Router();
const router = require('express-promise-router')();
const userController = require('../controllers/users');
router.route('/')
    .get(userController.index)
    .post(userController.newUser);
module.exports = router;

验证try cach 能捕获 错误，修改 routers/users.js

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//routers/users.js代码片段
    index: async (req,res,next) => {
        //Async-Await 方式
        try {
            const users = await User.find();
            throw new Error('Dummy error !');
            res.status(200).json(users);
        } catch (error) {
            next(error);
        }
    }

在 app.js 中，最后一个中间件，将错误捕获

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//app.js 代码片段
//Error handler function
app.use((err,req,res,next) => {
    //Response to client
    const error = app.get('env') === 'development' ? err : {};
    const status = err.status || 500;
    //Reponse to ourselves
    res.status(status).json({
        error:{
            message: error.message
        }
    });
});

在postman get /user 的结果

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{"error":{"message":"Dummy error !"}}

去除 routers/users.js 中的try catch 如下

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 //...
    index: async (req,res,next) => {
        //Async-Await 方式
        const users = await User.find();
        throw new Error('Dummy error !'); //仍旧能捕获错误
        res.status(200).json(users);
        //没有写next(err)
    }
//...

附代码
https://github.com/monk8/expressjs-rest-api-server/tree/lesson05

视频教程
https://www.bilibili.com/video/av11683622/#page=5