MongooseJS modify document during pre hook

Question

I'm having some issues with mongoose. My goal is that during pre-save, I would be able to modify the object, doing things like splitting the tags if needed, or in another case calculating the summation of a sub-document durations and update it within the main document.

What I'm finding is that if I load a model, then call doc.update passing the new data, only schema.pre('update', ...) triggers, and any changes to this within my middleware are not updated. I also tried using this.set('...', ....); within my update middleware to no avail.

It seems if I do doc.save(...) instead, then changes to this within schema.pre('save', ...) are appended as expected. Aside from extending the posted variables into my model's properties and saving, I'm not seeing any way of leveraging doc.update for this purpose.

My Goals: - Update an existing document via doc.update(properties, ....) - Use middleware during saving to modify the document, do advanced validation, and update related documents - Use middleware during updating to modify the document, do advanced validation, and update related documents - Interchangeably use model.findByIdAndUpdate, model.save, model.findById->doc.update, model.findById->doc.save and all tap into my save/update middleware.

Some arbitrary sample code:

function loadLocation(c) {
    var self = this;
    c.Location.findById(c.params.id, function(err, location) {
        c.respondTo(function(format) {
            if (err | !location) {
                format.json(function() {
                    c.send(err ? {
                        code: 500,
                        error: err
                    } : {
                        code: 404,
                        error: 'Location Not Found!'
                    });
                });
                format.html(function() {
                    c.redirect(c.path_to.admin_locations);
                });
            } else {
                self.location = location;
                c.next();
            }
        });
    });
}

LocationController.prototype.update = function update(c) {
    var location = this.location;
    this.title = 'Edit Location Details';

    location.update(c.body.Location, function(err) {
        c.respondTo(function(format) {
            format.json(function() {
                c.send(err ? {
                    code: 500,
                    error: location && location.errors || err
                } : {
                    code: 200,
                    location: location.toObject()
                });
            });
            format.html(function() {
                if (err) {
                    c.flash('error', JSON.stringify(err));
                } else {
                    c.flash('info', 'Location updated');
                }
                c.redirect(c.path_to.admin_location(location.id));
            });
        });
    });
};

module.exports = function(compound) {
    var schema = mongoose.Schema({
        name: String,
        address: String,
        tags: [{ type: String, index: true }],
        geo: {
            type: {
                type: String,
            default:
                "Point"
            },
            coordinates: [Number] // Longitude, Latitude
        }
    });
    schema.index({
        geo: '2dsphere'
    });
    var Location = mongoose.model('Location', schema);
    Location.modelName = 'Location';
    compound.models.Location = Location;

    schema.pre('save', function(next) {
        if(typeof this.tags === 'string') {
            this.tags = this.tags.split(',');
        }
    });
};

==== * revised sample * ====

module.exports = function(compound) {
    var schema = mongoose.Schema({
        name: String,
        bio: String
    });

    schema.pre('save', function(next) {
        console.log('Saving...');
        this.bio = "Tristique sed magna tortor?"; 
        next();
    });

    schema.pre('update', function(next) {
        console.log('Updating...');
        this.bio = "Quis ac, aenean egestas?"; 
        next();
    });

    var Author = mongoose.model('Author', schema);
    Author.modelName = 'Author';
    compound.models.Location = Author;
};

Answer 1

pre hooks work for both doc.save() and doc.update(). In both cases this refers to the document itself.

Note that hooks need to be added to your schema before compiling your model.

schema.pre('save', function(next) {
    if(typeof this.tags === 'string') {
        this.tags = this.tags.split(',');
    }
});
var Location = mongoose.model('Location', schema);

Answer 2

Mongoose doesn't support hooks to the Model Update API. However, an update hook can be done via Monkey-patch. The Hooker NPM package is a good way of doing this cleanly.

The RESTeasy project which is a Boilerplate for Node REST APIs has code that demonstrates how to do it:

var hooker = require('hooker');

var BaseSchema = new mongoose.Schema({
  sampleString: {
    type: String
  }
});

var BaseModel = mongoose.model('Base', BaseSchema);

// Utilize hooks for update operations. We do it in this way because MongooseJS
// does not natively support update hooks at the Schema level. This is a way
// to support it.
hooker.hook (BaseModel, 'update', {
  pre: function () {
    // Insert any logic you want before updating to occur here
    console.log('BaseModel pre update');
  },
  post: function () {
    // Insert any logic you want after updating to occur here
    console.log('BaseModel post update');
  }
});

// Export the Mongoose model
module.exports = BaseModel;