Mongoose Schema：强制创建对象数组

Question

我的 Mongoose 架构如下所示：

var userSchema = mongoose.Schema({

  fbid       : String,
  googleid   : String,
  birthday   : String,
  email      : String,
  first_name : String,
  last_name  : String,
  gender     : String,
  age        : Number,
  location   : String,
  paid       : { type: Boolean, default: 0 },
  lessons: [
    { 
      name    : { type: String,  default: 'foobar1'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar2'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar3'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar4'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar5'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar6'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar7'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    },
    { 
      name    : { type: String,  default: 'foobar8'},
      sent    : { type: Boolean, default: 0 },
      read    : { type: Boolean, default: 0 },
      activity: { type: Boolean, default: 0 }
    } 
  ]

});

在执行new User() 时，lessons 数组的所有内容都会正确创建除了，该数组作为空数组返回，而不是使用默认值创建嵌套对象。

在执行new User() 时可以创建这些对象，但我希望这发生在模型本身中，因为所有用户都将拥有相同的lessons 和相同的初始值。

我怎样才能做到这一点？

Answer 1

以下链接有助于在 mongoose Schema 中设置嵌套数组的默认值。

set default values to mongoose arrays in node js

你可以这样做：

var lessonSchema = Schema({
    name: { type: String },
    sent: { type: Boolean },
    read: { type: Boolean },
    activity: { type: Boolean }
});

var userSchema = Schema({
    fbid: { type: String },
    googleid: { type: String },
    birthday: { type: String },
    email: { type: String },
    first_name: { type: String },
    last_name: { type: String },
    gender: { type: String },
    age: { type: Number },
    location: { type: String },
    paid: { type: Boolean, default: 0 },
    lessons: [lessonSchema]
});

userSchema.pre("save", function (next) {
    if (!this.lessons || this.lessons.length == 0) {
        this.lessons = [];
        this.lessons.push({
            "name": "football 1",
            "sent": true,
            "read": true,
            "activity": true
        })

         this.lessons.push({
            "name": "football 2",
            "sent": true,
            "read": true,
            "activity": true
        })

         this.lessons.push({
            "name": "football 3",
            "sent": true,
            "read": true,
            "activity": true
        })

         this.lessons.push({
            "name": "football 3",
            "sent": true,
            "read": true,
            "activity": true
        })
    }
    next();
});

Answer 2

您可以在架构中添加预保存挂钩

schema.pre('save', function(next) {
  if (this.isNew) {
    this.set('lessons', [ ... ]);
  }
  next();
});

更多信息在这里http://mongoosejs.com/docs/middleware.html

Answer 3

在你的架构声明中设置默认值：

var defaultLessons = [
    { 
      name    : 'foobar1',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar2',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar3',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar4',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar5',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar6',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar7',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    ,
    { 
      name    : 'foobar8',
      sent    : 0 ,
      read    : 0 ,
      activity: 0 
    } 
  ];

var userSchema = new mongoose.Schema({
  ...
  lessons: { type: [], default: defaultLessons}
});

另一种更结构化的方式是使用sub docs：

var lessonSchema = new mongoose.Schema({                                                                         
  name    : { type: String,  default: 'foobar'},
  sent    : { type: Boolean, default: 0 },
  read    : { type: Boolean, default: 0 },
  activity: { type: Boolean, default: 0 }
});

var defaultLessons = [ 
    {  
      name    : 'foobar1', 
    }, 
    {  
      name    : 'foobar2', 
    }, 
    {  
      name    : 'foobar3', 
    }, 
    {  
      name    : 'foobar4', 
    }, 
    {  
      name    : 'foobar5', 
    }, 
    {  
      name    : 'foobar6', 
    }, 
    {  
      name    : 'foobar7', 
    }, 
    {  
      name    : 'foobar8', 
    }  
  ];

var userSchema = new mongoose.Schema({
  ...
  lessons: { type: [lessonSchema], default: defaultLessons}
});

但是，上述方法在 mongoose 4+ 中不起作用，我已经尝试过 mongoose 3.8 好的。见this discussion。