validations: https://mongoosejs.com/docs/validation.html

instance methods: https://mongoosejs.com/docs/guide.html#methods

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错误信息一大堆，想看有用的信息？

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• Mongoose Schema Validatioins:

定义validation的条件，一旦违反了条件就会出错，require属性，如果没有填该属性，报错；如果添加schema没有预先定义的属性，不会报错，但是会忽略那个新加的属性，不会被保存到数据表中。 

直接运行node product.js

mongo

show dbs

use shopAPP

db.products.find()

product.js

  1 const mongoose = require('mongoose');
  2 mongoose.connect('mongodb://localhost:27017/shopApp', { useNewUrlParser: true, useUnifiedTopology: true }). //shopApp, use shopApp in mongo!!!
  3     .then(() => {
  4         console.log("CONNECTION OPEN!!!")
  5     })
  6     .catch(err => {
  7         console.log("OH NO ERROR!!!!")
  8         console.log(err)
  9     })
 10 
 11 const productSchema = new mongoose.Schema({
 12     name: {
 13         type: String,
 14         required: true,
 15         maxlength: 20
 16     },
 17     price: {
 18         type: Number,
 19         required: true,
 20         min: [0, 'Price must be positive ya dodo!']. //如果破坏了0这个规则，就会打印“Price must be positive ya dodo!”这个信息
 21     },
 22     onSale: {
 23         type: Boolean,
 24         default: false //如果不另外声明，返回默认值false
 25     },
 26     categories: [String],
 27     qty: {
 28         online: {
 29             type: Number,
 30             default: 0
 31         },
 32         inStore: {
 33             type: Number,
 34             default: 0
 35         }
 36     },
 37     size: {
 38         type: String,
 39         enum: ['S', 'M', 'L']
 40         //size的值只能在S, M, L三个选择中选
 41     }
 42 
 43 });
 44 
 45 //用户自己定义的方法， foundProduct.greet(), 这里调用了greet()，所以this代表foundProduct.
 46 productSchema.methods.greet = function () {
 47     console.log("HELLLO!!! HI!! HOWDY!!! ")
 48     console.log(`- from ${this.name}`)
 49 }
 50 
    //instance method
 51 productSchema.methods.toggleOnSale = function () {
 52     this.onSale = !this.onSale;//充当一个开关的作用，拨动一下是关，再拨动一下是开
 53     return this.save();//如果只运行this.save()，it probably takes time, 
 54     // 怎么解决呢？ return this one, and set await when calling foundProduct.toggleOnSale();
 55 }
 56 
 57 // instance method
 58 productSchema.methods.addCategory = function (newCat) {
 59     this.categories.push(newCat);//更新new category
 60     return this.save();
 61 }
 62 
    //static method
 63 productSchema.statics.fireSale = function () { //static, 针对于整个Model的方法，而不是某一个实例
 64     return this.updateMany({}, { onSale: true, price: 0 })
 65 }
 66 
 67 
 68 const Product = mongoose.model('Product', productSchema);  //products document created!!!
 69 
 70 
 71 const findProduct = async () => {
 72     const foundProduct = await Product.findOne({ name: 'Mountain Bike' });
 73     console.log(foundProduct)
 74     foundProduct.greet()
 75     await foundProduct.toggleOnSale();
 76     console.log(foundProduct)//这儿为什么又要显示一次？——foundProduct.toggleOnSale();之后save change了，可以看update的效果
 77     await foundProduct.addCategory('Outdoors')
 78     console.log(foundProduct)
 79 }
 80 
 81 Product.fireSale().then(res => console.log(res))
 82 //static methods: fireSale并不是针对与某一个实例对象，而是针对整个model： Product，可以用于批量增删改查
 83 //而instance method只是针对于某一个实例对象的操作
 84 
 85 findProduct();
 86 
 87 
 88 const bike = new Product({ name: 'Cycling Jersey', price: 28.50, categories: ['Cycling'], size: 'XS' })
 89 bike.save()
 90     .then(data => {
 91         console.log("IT WORKED!")
 92         console.log(data);
 93     })
 94     .catch(err => {
 95         console.log("OH NO ERROR!")
 96         console.log(err)
 97     })
 98 
 99 // runValidators: true必须加上，如果你希望更新的时候也遵循之前的规则！！！
100 Product.findOneAndUpdate({ name: 'Tire Pump' }, { price: 9 }, { new: true, runValidators: true })
101     .then(data => {
102         console.log("IT WORKED!")
103         console.log(data);
104     })
105     .catch(err => {
106         console.log("OH NO ERROR!")
107         console.log(err)
108     })