Flask Framework Cookbook - Second Edition

How to do it...

It is pretty easy to add validations to our WTForm fields. We just need to pass a validators parameter, which accepts a list of validators to be implemented. Each of the validators can have their own arguments, which enables us to control the validations to a great extent.

Let's modify our ProductForm object in the models.py class to have validations:

from decimal import Decimal 
from wtforms.validators import InputRequired, NumberRange 
 
class ProductForm(FlaskForm): 
    name = StringField('Name', validators=[InputRequired()]) 
    price = DecimalField('Price', validators=[ 
        InputRequired(), NumberRange(min=Decimal('0.0')) 
    ]) 
    category = SelectField( 
        'Category', validators=[InputRequired()], coerce=int 
    ) 

Here, we have the InputRequired ...