How can I implement validations in Flask ORM?

How can I implement validations in Flask ORM?

You can implement validations in Flask ORM by using the validators module from Flask-WTF or by defining custom validation methods in your model.

Can you give me an example of a validation for an email field?

Sure! You can use the Email validator from Flask-WTF like this:

from wtforms import StringField
from wtforms.validators import DataRequired, Email

class UserForm(FlaskForm):
    email = StringField('Email', validators=[DataRequired(), Email()])

What if I want to add a custom validation for a username?

You can create a custom validator function. For example:

def validate_username(form, field):
    if len(field.data) < 3:
        raise ValidationError('Username must be at least 3 characters long.')

class UserForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired(), validate_username])

Is there a way to validate multiple fields together?

Yes, you can use the @validates decorator from SQLAlchemy to validate multiple fields together in your model.