Why is 'password2' a string and not a reference to the field password2 itself? Can anyone explain this a bit more?

Hi Adam,

I agree that passing in a string to refer to the other password seems a bit odd, especially when we are setting all this up in the form class itself and the fields are all defined right there.

But I think the reason for using a string begins with the fact that the form will eventually be rendered in html, and every input element (i.e., field) must have a "name" attribute.

As far as I understand, when a form is constructed in Flask, the field variable name that you have used to define a specific field in the form class will automatically become the "name" attribute of its corresponding input element. So when we refer to another field in EqualTo(), we will be passing in the "name" of that input field, not the field variable itself, so a string will be required.

Hope this clears things up.

Adam,

The best answer to this is looking at the source code for the "EqualTo" validator: https://github.com/wtforms/wtforms/blob/283b2803206825158834f1828bbf749c129b7c47/src/wtforms/validators.py#L88

Another student asked why the "form" reference that's passed into validators makes it possible to validate based on the value of other fields as well. The perfect example of this is a password and confirm password field, where the validity of one field is dependent on another.

Two things about this source code: the validator is a class, not a function. Don't let this throw you. The call method is basically the same as the function validators we're writing in this class. They're creating a class here to allow you to pass arguments to the init method to customize the validator method.

Inside EqualTo, the call method uses that string instead of a reference to password2, and here you can see why. Internally, EqualTo is using that string as a key for the form parameter!

Hope this helps!