| Objectives |
|---|
| Create Mongoose schemas & models |
| Integrate Mongoose with Express |
| Make use of Mongoose model instances |
MongoDB is a no-SQL database. Mongoose is a library or "wrapper" that gives us a bunch of convenience methods for working with MongoDB records (kind of like jQuery's convenience methods for manipulating the DOM). Generally we will not be interacting directly with MongoDB, instead we'll be working with mongoose.
Side-note: Wondering what makes noSQL different from SQL? (we'll talk more about this later)
There are two main categories of databases: relational (SQL) databases, and non-relational (no-SQL) databases. Mongo is a no-SQL database that stores entries in a JSON-like format.
Since Mongo is the first database we've worked with it's hard for us to discuss the tradeoffs between SQL/no-SQL. But here's a great analogy from a fellow on StackOverflow:
"NoSQL databases store information like you would recipes in a book. When you want to know how to make a cake, you go to that recipe, and all of the information about how to make that cake (ingredients, preparation, mixing, baking, finishing, etc.) are all on that one page.
SQL is like shopping for the ingredients for the recipe. In order to get all of your ingredients into your cart, you have to go to many different aisles to get each ingredient. When you are done shopping, your grocery cart will be full of all the ingredients you had to run around and collect.
Wouldn’t it be nicer if there was a store that was organized by recipe, so you could go to one place in the store and grab everything you need from that one spot? Granted you’ll find ingredients like eggs in 50 different places, so there’s a bit of overhead when stocking the shelves, but from a consumer standpoint it would be much easier/faster to find what they're looking for."
Let's do a quick activity and get Mongoose and Mongo setup on our machines.
- Assuming you already have MongoDB installed (you did this at installfest), to get started using mongoose in a project, we have to install it in our
package.json:
npm install --save mongoose- Next we need to
requireMongoose in our project andconnectto the MongoDB service (it could be local or hosted). We can do this inserver.jsfor now. Later we'll do it inmodels/index.js.
var mongoose = require('mongoose');
mongoose.connect('mongodb://localhost/todo-app-demo');What's a connection string?
mongodb://localhost/todo-app-demo is a string formatted by specifications provided by the Mongoose package in order to connect to a MongoDB database on your local system named todo-app-demo. You can name it whatever you like and it will be created as soon as you save some data to it.
- Finally, we need to run the MongodDB service. Generally you will want it open in a separate tab, running in the background.
mongodNote: If you already have an instance of MongoDB running, you'll get an error at this step. If that's the case, you can move on to the next step, since MongoDB is already running!
Running your MongoDB service is no different from running your Express server! nodemon runs your back-end server; mongod runs your MongoDB database.
Once you've finished the above steps, here's how you would set up an Express application with a "Todo" model (so we can start CRUDing todos!).
- In your Express application, create a folder called
modelswith a file for your first model. In the example, we have aTodomodel, so the filename istodo.js. Your folder structure should look similar to this:
your-app-name
├── models
│ └── todo.js
├── public
│ ├── scripts
│ │ └── main.js
│ └── styles
│ └── main.css
├── views
│ └── index.html
├── .gitignore
├── package.json
├── README.md
└── server.js
var mongoose = require('mongoose'),
Schema = mongoose.Schema;
var TodoSchema = new Schema({
task: String,
description: String
});
var Todo = mongoose.model('Todo', TodoSchema);
module.exports = Todo;- In
server.js, require your model.
// server.js
// Note without requiring your models you can't use them in server.js!
var Todo = require('./models/todo');Schema: Similar to an object constructor, a Schema is a diagram or blueprint for what every object in the noSQL database will contain. Here's an example of a simple Address Book noSQL database schema:
var ContactSchema = new Schema({
firstName: String,
lastName: String,
address: String,
phoneNumber: Number,
email: String,
professionalContact: Boolean
});With the above Schema, we can expect that all of our Address Book entries would have a first name, last name, address, and email address in the form of Strings. We can count on the phoneNumber to always be accepted, stored, and returned as a number. Lastly, the boolean value of Professional Contact will always be a true or false
Model: A model is a Schema that has been 'activated' with real data and is performing actions such as reading, saving, updating, etc.
var Contact = mongoose.model('Contact', ContactSchema);Every model instance that we store in the database is assigned an ID. In mongo that actually means an _id. We can use this ID later to look up a particular record. Later on we'll look at how we can use those IDs can help us form relationships in the database.
Most databases also require that we specify the data-type for each attribute. In mongoose we can use data-types from javascript such as String, Number, and even Array.
Let's look at this example:
// models/person.js
var mongoose = require('mongoose'),
Schema = mongoose.Schema;
var personSchema = new mongoose.Schema({
firstName: String,
lastName: String,
age: Number,
superPower: String,
weakness: String,
isExcited: Boolean
});
var Person = mongoose.model('Person', personSchema);
module.exports = Person;In the above note how we've assigned String, Number and even a Boolean as the data-types for this Schema.
Let's create an instance of this model.
// server.js
var Person = require('./models/person');
var justin = new Person({
firstName: "Justin",
lastName: "Castilla",
age: 33,
superPower: "Beard",
weakness: "Razors",
isExcited: true
});
justin.save(function(err, newPerson){
if(err) {return console.log(err);}
console.log("saved new person: ", newPerson);
});The above logs to the terminal the newPerson success object:
saved new person: {
__v: 0,
firstName: 'Justin',
lastName: 'Castilla',
age: 33,
superPower: 'Beard',
weakness: 'Razors',
isExcited: true,
_id: 57866b9f9d89c840336a135e }
Notice that mongo has added an _id and __v attributes.
We can use .find() to get all documents in the collection.
// get all todos
app.get('/api/todos', function todosIndex(req, res) {
// find all todos in db
Todo.find(function handleDBTodosListed(err, allTodos) {
res.json({ todos: allTodos });
});
});Note: We can also use .find() to get a specific set of documents in the collection (rather than ALL documents) by setting conditions. Read more in the docs.
We've seen the `new` keyword before! It creates new instances of an object. We use it here to create new instances of our `Todo` model. We then call `.save()` to store the new todo in our database.
// create new todo
app.post('/api/todos', function todosCreate(req, res) {
// create new todo with form data (`req.body`)
var newTodo = new Todo(req.body);
// save new todo in db
newTodo.save(function handleDBTodoSaved(err, savedTodo) {
res.json(savedTodo);
});
});We can use .findOne() to return the first document in the collection that matches certain criteria. In this case, we're looking for a todo that has a certain `_id`.
// get one todo
app.get('/api/todos/:id', function (req, res) {
// get todo id from url params (`req.params`)
var todoId = req.params.id;
// find todo in db by id
Todo.findOne({ _id: todoId }, function (err, foundTodo) {
res.json(foundTodo);
});
});Note: The .findById() method will also return a single document matching a specified id field.
Similar to the last example, we can use `.findOne()` to find the document with a certain `_id`. After updating the document, we use `.save()` to persist our changes to the database.
// update todo
app.put('/api/todos/:id', function (req, res) {
// get todo id from url params (`req.params`)
var todoId = req.params.id;
// find todo in db by id
Todo.findOne({ _id: todoId }, function (err, foundTodo) {
// update the todos's attributes
foundTodo.task = req.body.task;
foundTodo.description = req.body.description;
// save updated todo in db
foundTodo.save(function (err, savedTodo) {
res.json(savedTodo);
});
});
});The .findOneAndRemove() method takes care of finding the document with a certain `_id` and removing it from the database.
// delete todo
app.delete('/api/todos/:id', function (req, res) {
// get todo id from url params (`req.params`)
var todoId = req.params.id;
// find todo in db by id and remove
Todo.findOneAndRemove({ _id: todoId }, function (err, deletedTodo) {
res.json(deletedTodo);
});
});Note: Another way to remove the document is by finding the document first (using .findOne() or .findById()) and calling .remove().
Exploring your databases with the MongoDB shell can be a chore. Robomongo is a free application that can make it a little easier on you: Setting up Robomongo.
See your class schedule or Instructor for today's challenges!