Seeding MongoDB using Mongoose models

Question

I'm using mongoose to seed a mongodb database based on my mongoose models. I'm particular interested in improving the seed code.

I have two models, an article and a category. The relationship between the models are as follows:

A category has many articles An article has a parent category

The model schemas I'm using are listed below:

The category schema

var mongoose = require('mongoose');

var categorySchema = mongoose.Schema({
    title: String,
    articles : [{ type: mongoose.Schema.Types.ObjectId, ref: 'Article' }]
});

mongoose.model('Category', categorySchema);

The article schema

var mongoose = require('mongoose');

var articleSchema = mongoose.Schema({
    category: { type: mongoose.Schema.Types.ObjectId, ref: 'Category' },
    title: String
});

mongoose.model('Article', articleSchema);

I'm using the following code to seed:

Seeding the category

var CategoryModel = require('mongoose').model('Category');

exports.seedCategories = function seedCategories() {
    CategoryModel.find({}).exec(function (err, collection) {
        if (collection.length === 0) {
            CategoryModel.create({ title: 'Category One' });
            CategoryModel.create({ title: 'Category Two' });
        }
    });
}

Seeding the article

var CategoryModel = require('mongoose').model('Category');
var ArticleModel = require('mongoose').model('Article');

exports.seedArticles = function seedArticles() {

    ArticleModel.find({}).exec(function (err, collection) {
        if (collection.length === 0) {
            seedArticle('Category One', 'Article One');
            seedArticle('Category One', 'Article Two');
            seedArticle('Category Two', 'Article Three');
            seedArticle('Category Two', 'Article Four');
        }
    });

    function seedArticle(categoryTitle, articleTitle) {
        var parentCategory;
        CategoryModel.findOne({ title: categoryTitle }).exec()
            .then(function (category) {
                parentCategory = category;
                return ArticleModel.create({ title: articleTitle, _category: parentCategory._id });
            }).then(function (article) {
                parentCategory.articles.push(article._id);
                parentCategory.save(function (saveError) {
                    if (!saveError) {
                        console.log("Seeded article");
                    } else {
                        console.log(saveError);
                    }
                });
            });
    }
}

I'm particularly interested in methods for preventing the Christmas tree of doom, and removing the obstruent error handling. Any recommendations are welcome, and thanks in advance for the help. I hope this code helps others.

Mongoose have just implemented promises returned from saves, so that should help. It will be available in mongoose 3.10.

Answer 1

It seems that you are storing the data with double links (article -> category AND category -> articles).

I assume that you need to report on articles for a category. I would simple create an index on Category like this:

var articleSchema = mongoose.Schema({
    category: { type: mongoose.Schema.Types.ObjectId, ref: 'Category', index: true },
    title: String
});

This way you can simplify your code a ton by keeping it KISS:

function seedArticle(categoryTitle, articleTitle) {
  CategoryModel.findOne({ title: categoryTitle }).exec()
    .then(function (category) {
      return ArticleModel.create({ title: articleTitle, category: category._id });
    });
}

Other than that, I like your code.