node.js - Mongoose 原型(prototype): how to insert an url dynamically?

Question

我尝试为 Mongoose 模式创建一个原型(prototype)。数据库包含一行图片列表。

示例:

{
  "_id": ObjectId("55814a9799677ba44e7826d1"),
  "album": "album1",
  "pictures": [
    "1434536659272.jpg",
    "1434536656464.jpg",
    "1434535467767.jpg"
  ],
  "__v": 0
}

如果知道如何为每张图片注入(inject)一个 URL(例如原型(prototype))，以及如何以 JSOn 格式(用于 API)从集合中获取所有数据(包含图片和 url)，那就太棒了。

我测试了很多不同的方法，但它不起作用。

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

var PicturesSchema = new Schema({
    album: { type: String, required: true, trim: true },
    pictures: { type: Array, required: false, trim: true }
});

var Pictures = mongoose.model('Pictures', PicturesSchema);

// Not working
Pictures.prototype.getPics = function(){
    return 'https://s3.amazonaws.com/xxxxx/'+ this.pictures;
}

module.exports = Pictures;

如何“虚拟”注入(inject)每张图片的 URL(我不想将 URL 存储在数据库中)？

Answer 1

这是一个使用 an instance method 的示例:

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

var PicturesSchema = new Schema({
  album    : { type : String, required : true,  trim : true },
  pictures : { type : Array,  required : false, trim : true }
});

// Make sure this is declared before declaring the model itself.
PicturesSchema.methods.getPics = function() {
  // `this` is the document; because `this.pictures` is an array,
  // we use Array.prototype.map() to map each picture to an URL.
  return this.pictures.map(function(picture) {
    return 'https://s3.amazonaws.com/xxxxx/'+ picture;
  });
};

var Pictures = mongoose.model('Pictures', PicturesSchema);

// Demo:
var pictures = new Pictures({
  album    : 'album1',
  pictures : [
    '1434536659272.jpg',
    '1434536656464.jpg',
    '1434535467767.jpg'
  ]
});

console.log( pictures.getPics() );

如果您希望 URL 成为文档对象的一部分(例如，用作 JSON 响应)，请使用 "virtual"相反:

...
PicturesSchema.virtual('pictureUrls').get(function() {
  return this.pictures.map(function(picture) {
    return 'https://s3.amazonaws.com/xxxxx/'+ picture;
  });
});
...

// Demo:
console.log('%j', pictures.toJSON({ virtuals : true }) );