CRUD: Eliminar datos en Flask

Data management in web applications is a critical component for developers. In this article, we will explore how to implement delete functionality in a CRUD (Create, Read, Update, Delete) using a Python web framework. You will learn how to create specific paths, handle forms and confirm delete actions, thus completing your note management system.

How to implement the delete functionality in our CRUD?

To complete our CRUD system for notes, we need to implement the delete functionality. This process requires creating a new view and properly configuring the forms to handle deletion requests securely and efficiently.

Creating the path to delete notes

To delete a note, we need to create a new route in our application. Unlike routes to get information, deletion is handled mainly with the POST method, since we do not need to get data, but confirm the deletion action.

The basic structure of our delete route will be similar to the edit route, but with some key differences:

@app.route('/delete-note/<int:id>',  methods=['POST'])def delete_note(id): note = Note.query.get(id)    
 if not note: # If the note does not exist, there is no point in trying to delete it return redirect(url_for('home'))    
 db.session.delete(note) db.session.commit()    
 return redirect(url_for('home'))

Important things to consider:

• We use only the POST method for security.
• We verify that the note exists before trying to delete it.
• We use db.session.delete() passing the instance of the model
• Commit the changes with commit()
• Redirect the user to the home page

Implementing the deletion form

To activate the delete path from our interface, we need to create a form on the main page. This allows us to send a POST request to the delete path when the user wants to delete a note.

<form method="post" action="/delete-note/{{ note.id }}"> <button type="submit">Delete</button></form>.

This form must be included for each note displayed in the list. The action attribute must point to the delete URL with the specific ID of each note, while the method must be POST to match our path configuration.

Verifying operation

To verify that our implementation is working correctly, we can:

1. Inspect the generated HTML to verify that each form has the correct URL.
2. Use the browser's development tools (Network tab) to observe the requests
3. Confirm that after deleting a note, the page reloads without showing the deleted note.

Clicking the "Delete" button will send a POST request to our route, which will process the deletion and redirect the user to the updated home page.

How to improve the user experience when deleting items?

The basic implementation works, but we can improve it by adding a confirmation before permanently deleting a note. This avoids accidental deletions and improves the user experience.

Implementation of a confirmation alert

The proposed challenge is to display a confirmation alert before proceeding with the deletion. This involves modifying our current approach to include an additional step in the process.

Possible solutions:

1. Using JavaScript:

   function confirmDelete(event) { if (!confirm('Are you sure you want to delete this note?')) { event.preventDefault(); }}

2. Using an intermediate page:We could create an additional route that displays a confirmation page before proceeding with the deletion.

3. Using a modal:Implement a modal that appears when the delete button is clicked, with options to confirm or cancel.

Design and usability considerations.

When implementing the delete functionality, it is important to consider:

• Visual clarity: The delete button should be clearly distinguishable.
• Error prevention: Include confirmation to avoid accidental deletions.
• Feedback: Provide visual confirmation when a note has been deleted.
• Consistency: Maintain a consistent style with the rest of the application.

What have we learned about data management with SQL Alchemy?

Through the implementation of our full CRUD, we have learned how to perform the fundamental operations on a database using SQL Alchemy:

• Create: Insert new records into the database
• Read: Get and display existing data
• Update: Modify existing records
• Delete: Delete records from the database

SQL Alchemy provides us with an intuitive interface to interact with the database, allowing us to work with Python objects instead of writing SQL queries directly. This makes the code more maintainable and less error prone.

The database session(db.session) is a core component that allows us to perform operations such as:

• db.session.add() to add new objects.
• db.session.delete() to delete existing objects
• db.session.commit() to commit changes

Mastering these basic operations is critical to developing robust web applications that handle data efficiently and securely.

Developing a complete CRUD is an essential skill for any web developer. We encourage you to experiment with the suggested enhancements and share your solutions in the comments. What approach would you use to implement commit deletion?