限制架构参考猫鼬

Question

I have a Schema Device with the following property

user : { type: Schema.Types.ObjectId, ref: 'User', required: true }

and another Schema User with the following property:

device : [{ type: Schema.Types.ObjectId, ref: 'Device' }]

is it possible to limit the number of devices the user could have to 3?

Answer 1

Yes. What you need to do is add one validate property and pass validation function and the error message if the size exceed the max length Here I have given one function with the limit of 10. You can change it as per your requirement.

var UserSchema = new Schema({
    device: {
      type: [{
        type: Schema.Types.ObjectId,
        ref: 'Device'
      }],
      validate: [limit, '{PATH} exceeds the limit of 10']
    }
  });

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