如何在Mongoose模式中设置数组大小限制

Question

请您告诉我，在创建Mongoose模式时，有什么方法可以限制数组的大小。例如

 var peopleSchema = new Schema({
    name: {
        type: String,
        required: true,
        default: true
    },
   /* here I want to have limit: no more than 10 friends.
    Is it possible to define in schema?*/
    friends: [{
        type: Schema.Types.ObjectId,
        ref: 'peopleModel'
    }]
})

Answer 1

只需对架构设置做一个小小的调整，您就可以添加一个validate选项：

var peopleSchema = new Schema({
  name: {
    type: String,
    required: true,
    default: true
  },
  friends: {
    type: [{
      type: Schema.Types.ObjectId,
      ref: 'peopleModel'
    }],
    validate: [arrayLimit, '{PATH} exceeds the limit of 10']
  }
});

function arrayLimit(val) {
  return val.length <= 10;
}