Some questions regarding middleware

[imageck]

Howdies!

I never knew working with a database could be so fun! Mongoose is such a breath of fresh air.

Anyway, I was reading through the documentation and the concept of middleware has sparked my interest. Even though I haven't actually tried them yet I can see their use. Two questions remain:

1. Could someone please explain this bit about exports to me?

As a consequence, be careful about exporting Mongoose models from the same file that you define your schema. If you choose to use this pattern, you must define global plugins before calling require() on your model file.

const schema = new mongoose.Schema({ name: String });

// Once you `require()` this file, you can no longer add any middleware
// to this schema.
module.exports = mongoose.model('User', schema);

Does it simply imply that the set of middleware is immutable once the schema they're defined in is compiled the very first time? Meaning I won't be able to add new hooks or drop the existing ones should I decide to later on?

2. I have a collection of items with a tags key:

  tags: {
    type: [String],
    validate: {
      validator: a => a.length <= 10
    }
  },

but I'd also like to able to store them in their own collection. So a post-save hook seems like a perfect fit here. What would be a good way of achieving that? Export the Tag model in Item and do something like Tag.create() in the post-save hook?

Thanks!

[vkarpov15]

Thanks for your kind words, we're flattered :)

1. In general Mongoose doesn't support modifying the model's schema after compiling the model using mongoose.model() or Connection.prototype.model(). So that's why we recommend being careful about exporting mongoose.model() calls. However, there's a lot of workarounds.
2. Have a separate Tag model. I think Tag.findOneAndUpdate() with upsert in the Item schema's post('save') hook would be the easiest way to keep the Tag model in sync with the Item model.

[imageck]

Perfect! Thanks for the tips!