README.md

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Previously, you've learned, how to define routes in an Express.JS application. There we've also defined routes to create a TO-DO, update a TODO and to get details of a TO-DO. But the real implementation inside the callback function is not complete yet. And in this lesson we are about to do that. So, let's get started.

Video Script

Hey there, in this video we will write some logic inside our route definitions, to create and update a TO-DO. We will also use Sequelize to persist our data in PostgreSQL database. And to test our routes, we will respond back in JSON format, as our user interface is not ready yet.

Step 1: Define the TO-DO model using Sequelize

Before we can write logic inside our TO-DO endpoints, we have to define the TODO model using Sequelize.

To generate the Todo model, we will use the db:generate command of sequelize-cli. In this command, we have to pass the attributes of Todo along with their types. A Todo will have a title with type string, then dueDate of type date and a complete of type boolean.

npx sequelize-cli model:generate --name Todo --attributes title:string,dueDate:dateonly,completed:boolean

The above command will create a todo.js file in model folder and migration file in the migrations folder.

Action: Show both files in VS Code

Step 2: Create database table

The migration file has all the codes that we need to create the Todos table in the database. To simply run the migration file, we will execute the following command in the terminal:

npx sequelize-cli db:migrate

This will create the Todos table in the database.

Action: Show the Todos table using PGAdmin.

Step 3: Complete the create Todo endpoint implementation

In order to perform any operation for Todo, first we have to import the model in our primary index.js file.

const { Todo } = require("./models");

Next, in the create TODO endpoint, we have to read the request body to look for the To-Do title and dueDate.

Here we need the body-parser module to accept and parse JSON request body. Nowadays, the body-parser package comes by default with Express and we just have to require it:

const bodyParser = require('body-parser');
app.use(bodyParser.json());

Next, inside the create TO-DO route, we will use the .create() method from Sequelize, to insert a todo into the database, based on the request body:

app.post('/todos', async function (request, response) {
 console.log('Creating new Todo: ', request.body)
 try {
  const todo = await Todo.create({ title: request.body.title, dueDate: request.body.dueDate, completed: false })
  return response.json(todo);
 } catch (error) {
   console.log(error)
   return response.status(422).json(error);
 }
})

To test it out, first we have to make sure that the server is running:

node index.js

Then we will send a simple curl request from our terminal:

curl -d '{"title":"Go the gym","dueDate":"2022-07-02"}' -H "Content-Type: application/json" -X POST http://localhost:3000/todos

This curl call will create a new todo entry in our database, and will return the new database object to us.

We can further refractor the code by defining a addTodo class method in the Todo model, and moving the Todo.create method there itself.

  class Todo extends Model {
    /**
     * Helper method for defining associations.
     * This method is not a part of Sequelize lifecycle.
     * The `models/index` file will call this method automatically.
     */
    static associate(models) {
      // define association here
    }

    static addTodo({ title, dueDate }) {
      return this.create({ title: title, dueDate: dueDate, completed: false });
    }
  }

Here, inside the addTodo method, this refers to the class Todo itself.

Now we can call this class method addTodo from our route definition:

app.post('/todos', async function (request, response) {
  console.log('Creating new Todo: ', request.body)
  try {
    const todo = await Todo.addTodo(request.body);
    return response.json(todo);   
  } catch (error) {
    console.log(error)
    return response.status(422).json(error);    
  }
})

Step 4: Complete the markAsCompleted Todo endpoint implementation

To update the TO-DO that we've just created, we will use the .update() method of Sequelize.

But first, we have to find out the Todo that we want to update. In that case, we will use the findByPk method, where we have to pass the Todo ID that we are getting as part of the query parameter.

app.put('/todos/:id/markAsCompleted', async function (request, response) {
  console.log('We have to update a Todo with ID: ', request.params.id)
  const todo = await Todo.findByPk(request.params.id)
})

Next, we will define an instance method in Todo model named markAsCompleted, where we will actually update the Todo using .update()

  class Todo extends Model {
    /**
     * Helper method for defining associations.
     * This method is not a part of Sequelize lifecycle.
     * The `models/index` file will call this method automatically.
     */
    static associate(models) {
      // define association here
    }

    static addTodo({ title, dueDate }) {
      return this.create({ title, dueDate, completed: false });
    }

    markAsCompleted() {
      return this.update({ completed: true })
    }
  }

Here, inside the markAsCompleted method, this refers to an instance of class Todo. Now we can call this method from our route definition.

app.put('/todos/:id/markAsCompleted', async function (request, response) {
  console.log('We have to update a Todo with ID: ', request.params.id)
  const todo = await Todo.findByPk(request.params.id)
  try {
    const updatedTodo = await todo.markAsCompleted()
    return response.json(updatedTodo);
  } catch (error) {
    console.log(error)
    return response.status(422).json(error);   
  }
})

Let's test it out using curl:

curl -d '' -H "Content-Type: application/json" -X PUT http://localhost:3000/todos/1/markAsCompleted

Great! This request updates the to-do with ID 1 and sets completed as true.

That's all for this video, see you in the next one.