Pets Back-End Defining the Database

Learning objective: By the end of this lesson, students will be able to define and export a mongoose model for use with an API.

Create the model file `pet.js`

While this application will not have multiple models, it’s still a good idea to create a directory called models that will store all Mongoose models used in the application. Let’s go ahead and create the directory, along with our pet.js file inside of it:

mkdir models
touch models/pet.js

💡 We use a singular naming convention for model files, as a single file will always export just one model.

Create the pet schema

Before we’re able to define our model, we must first import the mongoose library into our pet.js file:

// models/pet.js

const mongoose = require('mongoose');

Next we’ll define the schema, which provides a consistent structure to our data.

In this case, our pet model will be pretty simple, with a name property of type String, an age property of type Number, and a breed property of type String. We’ll also specify that name and age are required fields, and give age a minimum value of 0.

Here’s how we’ll define that in our pet.js file:

// models/pet.js

const petSchema = mongoose.Schema({
  name: {
    type: String,
    required: true,
  },
  age: {
    type: Number,
    min: 0,
    required: true,
  },
  breed: String,
});

Register the model

Now that we’ve defined our schema, we’ll tell mongoose to create a collection in mongodb and validate that collection’s data using the schema. We do this using the mongoose.model method:

// models/pet.js
const Pet = mongoose.model('Pet', petSchema);

Export the model from the pet.js file

Next, we’ll export the Pet model we just created so that the rest of our application has access to it.

// models/pet.js

module.exports = Pet;

Our finished pet.js file will look like this:

// models/pet.js

const mongoose = require('mongoose');

const petSchema = mongoose.Schema({
  name: {
    type: String,
    required: true,
  },
  age: {
    type: Number,
    min: 0,
  },
  breed: String,
});

const Pet = mongoose.model('Pet', petSchema);

module.exports = Pet;

Import the model

Finally, we’ll need the Pet model in many of our routes, so let’s import it next. Similarly to our models directory, we’ll be using a controllers directory to help keep a clear separation of concerns. Let’s create that next:

mkdir controllers
touch controllers/pets.js

In controllers/pets.js, so let’s add an import statement to the top of that file:

// controllers/pets.js
const Pet = require('../models/pet.js');