Post init event does not fire after document creation

[ioncreature]

Here is CardType.js

var CardType = new Schema({
    name: {type: String, required: true},
    //...
});

CardType.post( 'init', function(){
    this._original = this.toObject();
});

I expect that all documents will have _original field

CardType.create( [{name: 'test'}, {name: 'test2'}], function( error ){
    var cardTypes = Array.prototype.splice.call( arguments, 1 );

    cardTypes.forEach( function( doc ){
        console.log( doc._original );
    });
});

doc._original always return undefined

Is it expected behavior or bug?

[vkarpov15]

Not sure, I'll investigate

[ioncreature]

I use version 3.8.17

[vkarpov15]

Hmm have you tried using the doc parameter?

CardType.post('init', function(doc) {
    doc._original = doc.toObject();
});

I'm not sure if this is the actual document in a post-save hook.

[ioncreature]

Да, Валерий.

I've tried to use that you said. But nothing happens.

// CardType.js
CardType.post( 'init', function( doc ){
    doc._original = doc.toObject();
    console.log( 'post init', doc.name );
});

There was no console output. So in my case post init handler did not fire at all.

[vkarpov15]

Hmm perhaps an exception is happening? Try putting the doc._original and console.log lines in a try/catch. I'm just confused because post('init') has test coverage, so this in theory shouldn't be happening.

Also, you might want to try upgrading to 3.8.18 - there was a minor bug related to .save() in 3.8.17 and create() calls save() under the hood

[ioncreature]

Result is the same, there is no changes in 3.8.18

Ok. I will show you all the real code:

// plugins/state.js
module.exports = function( schema ){
    schema.post( 'init', function( doc ){
        doc._original = doc.toObject();
        doc._isNew = doc.isNew;
    });

    schema.post( 'remove', function(){
        this._isRemoved = true;
    });
};

// CardType.js
var Schema = require( 'mongoose' ).Schema,
    util = require( '../util' ),
    statePlugin = require( './plugins/state' ),
    CardType = new Schema({
        name: {type: String, required: true},
        issuerId: {type: Schema.Types.ObjectId, ref: 'Issuer', index: true, required: true},
        magneticStripe: {type: Boolean, default: false},
        cardNumber: {type: Boolean, default: false},
        cardNumberLength: {type: Number, default: 0},
        userName: {type: Boolean, default: false},
        chip: {type: Boolean, default: false},
        nfc: {type: Boolean, default: false}
    });

CardType.plugin( statePlugin );

CardType.post( 'save', function( doc ){
    if ( doc._original && doc._original.name !== doc.name )
        this.model( 'Card' ).update( {typeId: doc._id}, {typeName: doc.name}, {multi: true}, util.noop );
});

module.exports = CardType;

// issuer.js
async.series({
    update: function( cb ){
        util.mixin( issuer, issuerData );
        issuer.save( cb );
    },
    cardTypes: function( cb ){
        CardType.create( cardTypes, cb );
    }
}, function( error, result ){
    // ...
});

But post init handler works fine when I write just:

var type = new CardType;
type.name = 'test';
type.issuerId = ObjectId.createFromTime( Date.now() );
type.save( handler );

Thanks.

[vkarpov15]

Turns out this is unfortunately expected behavior right now - init event is only emitted when a document is returned from the db, not when a document is created using new Model(). Somewhat wonky, I agree this should be changed.

[bshamblen]

Similar to the code in the original issue above I was storing a copy of the existing document in the post init hook, then in the pre save hook I was comparing the original document with the updated doc (if not new), then in the post save hook I had logic to send a notification of the changes.

As @ioncreature mentioned in his original post, this all used to work. Once I upgraded to 4.0 I received the same error message Object #<EventEmitter> has no method 'toObject'. I've been trying to come up with a workable solution, but I can't see a way to persist the original document through to the post save event.

My original code

schema.post('init', function() {
    this._original = this.toObject();
    this._changes = []; //array of objects with the path, new and old values. Populated by `observe` function in pre `save` hook
});

schema.pre('save', function(next) {
    //other logic here. Cut out for this example..

    this.observe(); //compares the current doc with the original and stores the new and old values in `this._changes` array.
    next();
});

schema.post('save', function(doc) {
    if (this._original && this._changes.length > 0) {
        //send web hook notification, with changes
    } else {
        //send web hook notification, with new document
    }

    //reset the values, in case the document is saved again.
    this._original = null;
    this._original = this;
    this._changes = [];
});

The problem with the new post init architecture is that if I now add a parameter to the hook function I can get the doc and add a copy to itself, but that copy will no longer be available in the pre or post save hooks.

Changed to

schema.post('init', function(doc) {
    doc._original = doc.toObject();
    doc._changes = [];
});

But in the pre save hook this._original is undefined, even for documents that we returned from the database. Any suggestions on how to reliably save a copy of the original document and have is survive the document lifecycle.

[vkarpov15]

Please open up a separate issue for that, that is an unrelated issue.

[ClaytonSmith]

Is there a workaround for this issue? I need a way to apply some foos and bars to my model's data only when the doc is first created.

[vkarpov15]

@ClaytonSmith schema.methods.foo = function() { this.bar = 'baz'; }; schema.queue('foo'); foo gets called every time a document with that schema is created.

[alecmev]

@vkarpov15 Please, update your last comment with a proper example of schema.queue usage, like here. This was quite misleading, considering that it can't be found in the docs.

Also, I'd like to note that it's synchronous only.

[vkarpov15]

@jeremejevs thanks for pointing this out, fixed 👍

[vkarpov15]

I'm going to close this for now, schema.queue() is the way to go.

[vkarpov15]

See https://mongoosejs.com/docs/api.html#schema_Schema-queue