Solicitudes DELETE

Data deletion is a fundamental operation in any application that handles information. In the context of web development, correctly implementing the delete functionality is essential to maintain data integrity and provide a complete user experience. This time, we will explore how to implement the DELETE operation in our CRUD (Create, Read, Update, Delete) using Node.js and file handling for local storage.

How to implement the DELETE operation in our CRUD?

To complete our CRUD, we need to implement the user delete functionality. This operation will allow us to delete specific records from our local file-based database. Let's create a new entry point in our application that will handle DELETE requests.

First, we create our file to handle the deletion:

// app.delete.jsapp.delete('/users/:id', (req, res) => { const userId = parseInt(req.params.id, 10);  
 fs.readFile(usersFilePath, 'utf8', (err, data) => { if (err) { return res.status(500).json({ error: "Error with data connection" }); }    
 let users = JSON.parse(data); users = users.filter(user => user.id !== userId);    
 fs.writeFile(usersFilePath, JSON.stringify(users, null, 2), (err) => { if (err) { return res.status(500).json({ error: "Error deleting user" }); }      
 res.status(204).send(); }); }); });});

In this code:

1. We create a dynamic path /users/:id that accepts the ID of the user to delete.
2. We extract the ID from the request parameters and convert it to a number.
3. Read the existing users file
4. Filter the list to exclude the user with the specified ID
5. Write the new list of users to the file
6. Respond with a code 204 (No Content) to indicate success with no return content

How does user filtering work?

The key part of our implementation is the filter() method that we use to remove the specific user:

users = users.filter(user => user.id !== userId);

This method creates a new array that includes all the elements that pass the specified condition. In our case, we are keeping all the users whose ID does not match the ID we want to remove. In this way, we effectively remove the desired user from the array.

It is important to understand that this approach does not modify the original array, but creates a new one without the element we want to remove. This follows the principle of immutability which is a good programming practice.

How do we test our delete functionality?

To test our implementation, we use Postman:

1. We create a new request
2. Select the DELETE method
3. We set the URL with the ID of the user we want to delete (for example: /users/2)
4. We do not need to send any body in the request
5. Send the request and verify that we receive a 204 status code.

If everything works correctly, the user with the specified ID will be removed from our users file.

How does DELETE integrate with the other CRUD operations?

With the implementation of DELETE, we now have a complete CRUD for our application:

• Create: Implemented with POST to add new users.
• Read: Implemented with GET to get users
• Update: Implemented with PUT to update users (with a pending challenge)
• Delete: Implemented with DELETE to delete users

Each of these operations follows a similar pattern:

1. Receive an HTTP request
2. Read the existing data file
3. Perform the corresponding operation (create, read, update or delete)
4. Write the changes back to the file (except for read operations)
5. Respond with the appropriate status code and data

What challenges remain?

As mentioned in the class, there is one remaining challenge related to the update (PUT) functionality. The problem is related to the handling of duplicate IDs. The solution involves modifying the update logic to ensure that:

1. Only the correct user is updated when there are multiple users with the same ID.
2. Data integrity is maintained during the update.

This is an excellent exercise to practice data manipulation and programming logic.

What's next after implementing the full CRUD?

Once we have our basic CRUD up and running, we can move on to more advanced concepts such as:

1. Implementing middlewares to handle common functionality.
2. Setting up logging systems to track activities and errors
3. Improving data validation
4. Implementing authentication and authorization
5. Performance optimization

These topics will allow us to build more robust, secure and maintainable applications.

Implementing a complete CRUD is an important milestone in web application development. With these basic operations, we can build complex systems that allow users to interact with data effectively. Have you implemented any interesting solutions to the upgrade challenge? Share your ideas and solutions in the comments.