貓鼬虛擬領域與異步getter

Question

我有一個項目模型，其中有一個虛擬字段來引用股票徽章。

'use strict';

const mongoose = require('mongoose');
const mongooseHidden = require('mongoose-hidden')();
const Badge = mongoose.model('Badge');

const validateProperty = function(property) {
  return (property.length);
};

const Schema = mongoose.Schema;

const ItemSchema = new Schema({
  itemCode: {
    type: Number,
    index: {
      unique: true,
      sparse: true // For this to work on a previously indexed field, the index must be dropped & the application restarted.
    },
    required: true
  },
  itemName: {
    type: String,
    uppercase: true,
    trim: true
  },
  barcode: {
    type: String,
    trim: true
  },
  category: {
    type: Schema.Types.ObjectId,
    ref: 'Category'
  },
  subCategory: {
    type: Schema.Types.ObjectId,
    ref: 'SubCategory'
  },
  updated: {
    type: Date
  },
  created: {
    type: Date,
    default: Date.now
  },
  status: {
    type: String,
    enum: [
      'active', 'inactive', 'removed'
    ],
    default: 'active'
  }
}, {id: false});

ItemSchema.virtual('badges').get(function() {
  return this.getAvailableBadges();
});

ItemSchema.methods.getAvailableBadges = function() {
  Badge.find({
    item: this._id
  }, (err, badges) => {
    if (badges) {
      return badges;
    } else {
      return [];
    }
  });
};

ItemSchema.set('toJSON', {virtuals: true});
ItemSchema.set('toObject', {virtuals: true});

ItemSchema.plugin(mongooseHidden, {
  hidden: {
    _id: false,
    __v: true
  }
});

mongoose.model('Item', ItemSchema);

和批處理模型如下

'use strict';

const mongoose = require('mongoose');
const mongooseHidden = require('mongoose-hidden')();

const validateProperty = function(property) {
  return (property.length);
};

const Schema = mongoose.Schema;

const BadgeSchema = new Schema({
  item: {
    type: Schema.Types.ObjectId,
    ref: 'Item'
  },
  qty: {
    type: Number,
    validate: [validateProperty, 'Please enter Quantity !']
  },
  purchasingPrice: {
    type: Number,
    validate: [validateProperty, 'Please enter purchasingPrice !']
  },
  sellingPrice: {
    type: Number,
    validate: [validateProperty, 'Please enter sellingPrice !']
  },
  updated: {
    type: Date
  },
  created: {
    type: Date,
    default: Date.now
  },
  status: {
    type: String,
    enum: [
      'active', 'inactive', 'removed'
    ],
    default: 'active'
  }
});

BadgeSchema.plugin(mongooseHidden, {
  hidden: {
    _id: false,
    __v: true
  }
});

mongoose.model('Badge', BadgeSchema);

物品的徽章虛擬字段未填充。

我們如何使用異步getter方法

我放置了一些控制台日志語句，發現getAvailableBadges正在獲取數據。

我需要通過express發送帶有虛擬字段值的json對象。 我該怎么做？

Answer 1

我所做的就是創建一個虛擬財產

ItemSchema.virtual('badges', {
  ref: 'Badge',
  localField: '_id',
  foreignField: 'item'
});

並用

{
   path: 'badges',
   select: [
     'qty', 'purchasingPrice', 'sellingPrice'
   ],
   options: {
     sort: {
       'created': -1
     }
   }
}

Answer 2

好吧，這些操作是異步的，因此您必須等待回調觸發。

您只能通過在回調中傳遞值來返回值（或者可以在調用回調之前設置當前對象的值）。

我認為應該是這樣的：

ItemSchema.virtual('badges').get(function (callback) {
    Badge.find({ item: this._id }, callback);
};

然后你會用它像

item.badges(function (err, badges) {
    // do something with badges
});