Using Flask Wtforms Validators Without Using A Form

I'm receiving user registration data from an iOS application and I'd like to use the validators that come with wtforms to make sure the email and password are acceptable. However,

Solution 1:

Yes, this is entirely possible - the wtforms.Form constructor takes any MultiDict like interface (it just needs to have getlist), so you can just create an instance of werkzeug.datastructures.MultiDict from your JSON:

data = MultiDict(mapping=request.json)
form = YourForm(data)
if form.validate():
    # Data is correct

(assuming the field names match) and things will just work.

Solution 2:

Here's a little utility called Flask-Inputs that I'm working on to solve this. The goal is to allow all incoming data (forms, queries, headers, etc) to be validated with wtform validators.

Here's how validation would work with your data:

from flask_inputs import Inputs
from wtforms.validators import Length, Email, ValidationError


classRegisterInputs(Inputs):
    json = {
        'email': [Email(), unique_email],
        'username': [Length(min=3, max=15), unique_username]
    }

defunique_email(form, field):
    if User.query.filter_by(email=field.data).first():
        raise ValidationError('Email is already registered.')

defunique_username(form, field):
    if User.query.filter_by(username=field.data).first():
        raise ValidationError('Username is already registered.')


@auth.route('/register', methods=['POST'])defregister():
    inputs = RegisterInputs(request)

    if inputs.validate():
        user = User.register_fromJSON(request.json)

        db.session.add(user)
        db.session.commit()

        return jsonify(success=1)
    else:
        return jsonify(failure=0, errors=inputs.errors)