OverwriteModelError：编译后无法覆盖`Product`模型答案

【问题标题】：OverwriteModelError: Cannot overwrite `Product` model once compiledOverwriteModelError：编译后无法覆盖`Product`模型
【发布时间】：2017-10-04 08:50:51
【问题描述】：

我曾尝试在我的 purchaseSchema 中调用我的 productSchema，但出现此错误：OverwriteModelError: Cannot overwrite Product model 一旦编译。我可以尝试什么？

这是我的产品架构：

mongoose = require('mongoose');
var Schema = mongoose.Schema;

var productSchema = new Schema({

cd: {
    type: Number,
    require: true
},

nm_iten: {
    type: String,
    require: true
},

type_iten: {
    type: String,
    require: true
},

unity: {
    type: String,
    require: true
},

});
var product = mongoose.model('Product',productSchema);
module.exports = {product:product}

而且，这是我购买的 Schema：

   var mongoose = require('mongoose');
   var Schema = mongoose.Schema;
   var productSchema = require('./products');
   var product = productSchema.product;

   var purchaseSchema = new Schema({

     code: {
       type: Number,
       require: true
    },

     product:[product],

     quant: {
       type: Number,
       require: true
    },

    vl_uni: {
       type: Number,
       require: true
     },

     vl_total: {
        type: Number,
        require: true
    }


    });
    mongoose.model('Purchase',purchaseSchema);

【问题讨论】：

标签： javascript node.js mongodb express mongoose

【解决方案1】：

在购买模式中，product 需要指向 productSchema，而不是产品模型。

产品架构：

mongoose = require('mongoose');
var Schema = mongoose.Schema;

var productSchema = new Schema({
    cd: {
        type: Number,
        require: true
    },    
    nm_iten: {
        type: String,
        require: true
    },       
    type_iten: {
        type: String,
        require: true
    },        
    unity: {
        type: String,
        require: true
    },   
});
module.exports = productSchema;

购买模式：

var mongoose = require('mongoose');
var Schema = mongoose.Schema;
var productSchema = require('./products');
var product = productSchema;

var purchaseSchema = new Schema({
   code: {
       type: Number,
       require: true
   },
   product:[product],
   quant: {
       type: Number,
       require: true
   },
   vl_uni: {
       type: Number,
       require: true
   },
   vl_total: {
       type: Number,
       require: true
   }
});
mongoose.model('Purchase',purchaseSchema);

有关更多信息，请参阅有关嵌入式文档的 mongodb 文档： http://mongoosejs.com/docs/2.7.x/docs/embedded-documents.html

【讨论】：