Mongoose single embedded sub-document default

Question

Mongoose created a new single sub-document feature (documentation and feature request) in version 4.2.7 allowing for a single embedded sub document schema which behaves they way one-to-many sub documents behave.

What is the best way to create a default single sub-doc upon parent save?

var UserPermisssionsSchema = new mongoose.Schema({     siteAdmin: {         type: Boolean,         default: false,     } });  var UserSchema = mongoose.Schema({   fname: String,   lname: String,   permissions: UserPermisssionsSchema  }); 

I would like the permissions field to be created with default values when the parent user document is created.

This does not work:

var UserSchema = mongoose.Schema({   fname: String,   lname: String,   permissions: {     type: UserPermisssionsSchema ,     default: UserPermisssionsSchema   } }); 

Answer 1

Please try this one

var PerSchema = new mongoose.Schema({     siteAdmin: {type: Boolean, default: false}   });   var UserSchema = mongoose.Schema({   fname: String,   lname: String,   permissions: { type: PerSchema, default: () => ({}) }, }); 

Test it with Mongoose v4.4.3

var User = mongoose.model('User', UserSchema);  function setUser() {     var u = new User({         fname: 'asa',         lname: 'dddd'     });      u.save(function(err) {         if (err)             console.log(err);         else             console.log('save user successfully');     }); } 

Result is

{    "_id" : ObjectId("56c68321a548be98198ebb71"),    "fname" : "asa",    "lname" : "dddd",    "permissions" : {        "_id" : ObjectId("56c68321a548be98198ebb70"),         "siteAdmin" : false        },    "__v" : 0 } 

---

If you want the default value of permissions is {}. Please try it as below

var PerSchema = mongoose.Schema({     siteAdmin: {type: Boolean} }, {_id: false});   var UserSchema = mongoose.Schema({     fname: String,     lname: String,     permissions: { type: PerSchema, required: true, default: {} }, });  

Test

function setUser() {     var u = new User({         fname: 'asa',         lname: 'dddd'     });      u.save(function(err) {         if (err)             console.log(err);         else             console.log('save user successfully');     }); } 

Result is

{ "_id" : ObjectId("56c687427191d54021875fb1"),    "fname" : "asa",    "lname" : "dddd",   "permissions" : {  },    "__v" : 0 } 

Answer 2

Mongoose maintainer here, I'd recommend this:

var UserSchema = mongoose.Schema({   fname: String,   lname: String,   permissions:      type: UserPermisssionsSchema ,     default: () => ({}),   } }); 

This will make permissions default to an empty object, with respect to any defaults the UserPermissionsSchema might have. If you set default to UserPermisssionsSchema you might get some bad behavior if one of your properties happens to overlap with a mongoose schema method.