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diff --git a/app/static/doc/flask-docs/_sources/patterns/wtforms.txt b/app/static/doc/flask-docs/_sources/patterns/wtforms.txt new file mode 100644 index 0000000..93824df --- /dev/null +++ b/app/static/doc/flask-docs/_sources/patterns/wtforms.txt @@ -0,0 +1,124 @@ +Form Validation with WTForms +============================ + +When you have to work with form data submitted by a browser view code +quickly becomes very hard to read. There are libraries out there designed +to make this process easier to manage. One of them is `WTForms`_ which we +will handle here. If you find yourself in the situation of having many +forms, you might want to give it a try. + +When you are working with WTForms you have to define your forms as classes +first. I recommend breaking up the application into multiple modules +(:ref:`larger-applications`) for that and adding a separate module for the +forms. + +.. admonition:: Getting most of WTForms with an Extension + + The `Flask-WTF`_ extension expands on this pattern and adds a few + handful little helpers that make working with forms and Flask more + fun. You can get it from `PyPI + <http://pypi.python.org/pypi/Flask-WTF>`_. + +.. _Flask-WTF: http://packages.python.org/Flask-WTF/ + +The Forms +--------- + +This is an example form for a typical registration page:: + + from wtforms import Form, BooleanField, TextField, validators + + class RegistrationForm(Form): + username = TextField('Username', [validators.Length(min=4, max=25)]) + email = TextField('Email Address', [validators.Length(min=6, max=35)]) + password = PasswordField('New Password', [ + validators.Required(), + validators.EqualTo('confirm', message='Passwords must match') + ]) + confirm = PasswordField('Repeat Password') + accept_tos = BooleanField('I accept the TOS', [validators.Required()]) + +In the View +----------- + +In the view function, the usage of this form looks like this:: + + @app.route('/register', methods=['GET', 'POST']) + def register(): + form = RegistrationForm(request.form) + if request.method == 'POST' and form.validate(): + user = User(form.username.data, form.email.data, + form.password.data) + db_session.add(user) + flash('Thanks for registering') + return redirect(url_for('login')) + return render_template('register.html', form=form) + +Notice that we are implying that the view is using SQLAlchemy here +(:ref:`sqlalchemy-pattern`) but this is no requirement of course. Adapt +the code as necessary. + +Things to remember: + +1. create the form from the request :attr:`~flask.request.form` value if + the data is submitted via the HTTP `POST` method and + :attr:`~flask.request.args` if the data is submitted as `GET`. +2. to validate the data, call the :func:`~wtforms.form.Form.validate` + method which will return `True` if the data validates, `False` + otherwise. +3. to access individual values from the form, access `form.<NAME>.data`. + +Forms in Templates +------------------ + +Now to the template side. When you pass the form to the templates you can +easily render them there. Look at the following example template to see +how easy this is. WTForms does half the form generation for us already. +To make it even nicer, we can write a macro that renders a field with +label and a list of errors if there are any. + +Here's an example `_formhelpers.html` template with such a macro: + +.. sourcecode:: html+jinja + + {% macro render_field(field) %} + <dt>{{ field.label }} + <dd>{{ field(**kwargs)|safe }} + {% if field.errors %} + <ul class="errors"> + {% for error in field.errors %}<li>{{ error }}{% endfor %} + </ul> + {% endif %} + </dd> + {% endmacro %} + +This macro accepts a couple of keyword arguments that are forwarded to +WTForm's field function that renders the field for us. The keyword +arguments will be inserted as HTML attributes. So for example you can +call ``render_field(form.username, class='username')`` to add a class to +the input element. Note that WTForms returns standard Python unicode +strings, so we have to tell Jinja2 that this data is already HTML escaped +with the `|safe` filter. + +Here the `register.html` template for the function we used above which +takes advantage of the `_formhelpers.html` template: + +.. sourcecode:: html+jinja + + {% from "_formhelpers.html" import render_field %} + <form method="post" action="/register"> + <dl> + {{ render_field(form.username) }} + {{ render_field(form.email) }} + {{ render_field(form.password) }} + {{ render_field(form.confirm) }} + {{ render_field(form.accept_tos) }} + </dl> + <p><input type=submit value=Register> + </form> + +For more information about WTForms, head over to the `WTForms +website`_. + +.. _WTForms: http://wtforms.simplecodes.com/ +.. _WTForms website: http://wtforms.simplecodes.com/ |