Unable to update mongoose model

Question

I have a weird issue that is baffling me. I have a model:

var Model = new Schema({
    name: String,
    variations: Array
});

The variations entry looks like this:

[ {code: '', price: '' }, {code: '', price: '' }]

I need to add a new field - say "color". So I am doing this to batch update:

Model.find().exec(function(err, products) {
    if (!err) {
        products.forEach(function(p) {
            for(var i = p.variations.length - 1; i >= 0; i--) {
                p.variations[i]['color'] = 'red';
                // This shows all existing variations 
                // with the new color feed - correct
                console.log(p.variations[i]);
            }
            p.save(function(err) {
                if (!err) {
                    console.log("Success");
                } else {
                    console.log(err);
                }
            });
        });     
    }
});

However the "color" field is not set - if I go through again and comment out the p.variations[i]['color'] = 'red'; line then it does not show. I can't seem to figure out why it's doing this. I have an onSave event that is triggered correctly so it's saving. I also do not have any check on the variations structure - i.e. there is no code that only allows code and price. I'm obviously missing something but after a couple of hours I ran out of ideas.

Answer 1

When you modify the contents of an untyped Array field like variations, you need to notify Mongoose that you've changed its value by calling markModified(path) on the modified document or a subsequent save() call won't save it. See docs.

  for(var i = p.variations.length - 1; i >=0; i--) {
    p.variations[i]['color'] = 'red';
  }
  p.markModified('variations');
  p.save(function(err) { ...

Answer 2

You have to use the set function to change a property. The reasoning behind that is that mongoose has to mark the field as modified in order to be saved to the database.

for(var i = p.variations.length - 1; i >=0; i--) {
  p.variations[i].set({"color":"red", "code":"herr"});
  // or
  p.variations[i].set("color":"red");
  p.variations[i].set("code":"herr");
}

An alternative would be to change the field's value the old way, without going trought the setter, then manually mark it as modified: p.markModified('variations');

In my opinion you should always use the setter since this is more readable. You can just pass a json object containing all your changes in parameter and it will safely update the fields that you really want to change.