Creating Forms
**************


Secure Form
===========

Without any configuration, the "FlaskForm" will be a session secure
form with csrf protection. We encourage you not to change this.

But if you want to disable the csrf protection, you can pass:

   form = FlaskForm(meta={'csrf': False})

You can disable it globally—though you really shouldn't—with the
configuration:

   WTF_CSRF_ENABLED = False

In order to generate the csrf token, you must have a secret key, this
is usually the same as your Flask app secret key. If you want to use
another secret key, config it:

   WTF_CSRF_SECRET_KEY = 'a random string'


File Uploads
============

The "FileField" provided by Flask-WTF differs from the WTForms-
provided field. It will check that the file is a non-empty instance of
"FileStorage", otherwise "data" will be "None".

   from flask_wtf import FlaskForm
   from flask_wtf.file import FileField, FileRequired
   from werkzeug.utils import secure_filename

   class PhotoForm(FlaskForm):
       photo = FileField(validators=[FileRequired()])

   @app.route('/upload', methods=['GET', 'POST'])
   def upload():
       form = PhotoForm()

       if form.validate_on_submit():
           f = form.photo.data
           filename = secure_filename(f.filename)
           f.save(os.path.join(
               app.instance_path, 'photos', filename
           ))
           return redirect(url_for('index'))

       return render_template('upload.html', form=form)

Similarly, you can use the "MultipleFileField" provided by Flask-WTF
to handle multiple files. It will check that the files is a list of
non-empty instance of "FileStorage", otherwise "data" will be "None".

   from flask_wtf import FlaskForm
   from flask_wtf.file import MultipleFileField, FileRequired
   from werkzeug.utils import secure_filename

   class PhotoForm(FlaskForm):
       photos = MultipleFileField(validators=[FileRequired()])

   @app.route('/upload', methods=['GET', 'POST'])
   def upload():
       form = PhotoForm()

       if form.validate_on_submit():
           for f in form.photo.data:  # form.photo.data return a list of FileStorage object
               filename = secure_filename(f.filename)
               f.save(os.path.join(
                   app.instance_path, 'photos', filename
               ))
           return redirect(url_for('index'))

       return render_template('upload.html', form=form)

Remember to set the "enctype" of the HTML form to "multipart/form-
data", otherwise "request.files" will be empty.

   <form method="POST" enctype="multipart/form-data">
       ...
   </form>

Flask-WTF handles passing form data to the form for you. If you pass
in the data explicitly, remember that "request.form" must be combined
with "request.files" for the form to see the file data.

   form = PhotoForm()
   # is equivalent to:

   from flask import request
   from werkzeug.datastructures import CombinedMultiDict
   form = PhotoForm(CombinedMultiDict((request.files, request.form)))


Validation
----------

Flask-WTF supports validating file uploads with "FileRequired",
"FileAllowed", and "FileSize". They can be used with both Flask-WTF's
and WTForms's "FileField" and "MultipleFileField" classes.

"FileAllowed" works well with Flask-Uploads.

   from flask_uploads import UploadSet, IMAGES
   from flask_wtf import FlaskForm
   from flask_wtf.file import FileField, FileAllowed, FileRequired

   images = UploadSet('images', IMAGES)

   class UploadForm(FlaskForm):
       upload = FileField('image', validators=[
           FileRequired(),
           FileAllowed(images, 'Images only!')
       ])

It can be used without Flask-Uploads by passing the extensions
directly.

   class UploadForm(FlaskForm):
       upload = FileField('image', validators=[
           FileRequired(),
           FileAllowed(['jpg', 'png'], 'Images only!')
       ])


Recaptcha
=========

Flask-WTF also provides Recaptcha support through a "RecaptchaField":

   from flask_wtf import FlaskForm, RecaptchaField
   from wtforms import TextField

   class SignupForm(FlaskForm):
       username = TextField('Username')
       recaptcha = RecaptchaField()

This comes with a number of configuration variables, some of which you
have to configure.

+-------------------------+-------------------------------------------------------------------------------------------+
| RECAPTCHA_PUBLIC_KEY    | **required** A public key.                                                                |
+-------------------------+-------------------------------------------------------------------------------------------+
| RECAPTCHA_PRIVATE_KEY   | **required** A private key.                                                               |
+-------------------------+-------------------------------------------------------------------------------------------+
| RECAPTCHA_API_SERVER    | **optional** Specify your Recaptcha API server.                                           |
+-------------------------+-------------------------------------------------------------------------------------------+
| RECAPTCHA_PARAMETERS    | **optional** A dict of JavaScript (api.js) parameters.                                    |
+-------------------------+-------------------------------------------------------------------------------------------+
| RECAPTCHA_DATA_ATTRS    | **optional** A dict of data attributes options. https://developers.go                     |
|                         | ogle.com/recaptcha/docs/display#javascript_resource_apijs_parameters                      |
+-------------------------+-------------------------------------------------------------------------------------------+

Example of RECAPTCHA_PARAMETERS, and RECAPTCHA_DATA_ATTRS:

   RECAPTCHA_PARAMETERS = {'hl': 'zh', 'render': 'explicit'}
   RECAPTCHA_DATA_ATTRS = {'theme': 'dark'}

For your convenience, when testing your application, if "app.testing"
is "True", the recaptcha field will always be valid.

And it can be easily setup in the templates:

   <form action="/" method="post">
       {{ form.username }}
       {{ form.recaptcha }}
   </form>

We have an example for you: recaptcha@github.
