Alter field.data before validators for a DateField are called?

Question

My issue is very simple, here is a basic example:

class F(Form):
  date_test = DateField('Test', validators=[Required()], format='%d/%m/%Y')

I need to change the value sent by the user before the validators are called. What's the simplest way to do this without losing the benefits of using WTForms?

Answer 1

Actualy "filters" was nice but it was not exactly what I was trying to do. I made a custom field and it's working.

class MyDateField(DateField):
    def __init__(self, label='', validators=None, transform_data=False, **kwargs):
        super(MyDateField, self).__init__(label, validators, **kwargs)
        self.transform_data = transform_data

    def process_formdata(self, valuelist):
      if self.transform_data:
        data = str(valuelist[0])
        # transform your data here. (for example: data = data.replace('-', '.'))

      super(MyDateField, self).process_formdata([data])

class F(Form):
    date_test = MyDateField('Test', validators=[Required()], format='%d/%m/%Y', transform_data=True])

If you want to modify the value directly in the user field you need to override _value().

Answer 2

All WTForm fields should support the filters keyword argument, which is a list of callables that will be run on the input data:

def transform_data(data):
    # do something with data here
    return data

class F(Form):
    date_test = DateField('Test', validators=[Required()], format='%d/%m/%Y',
                              filters=[transform_data])