Dynamically generate flask-wtf form

Question

I have to make a lot of RadioFields, and I thought it would be good to dynamically generate them, but I can't get the code working. I'm using Flask and flask-wtf.

Form definition:

from flask_wtf import FlaskForm
from wtforms import RadioField, SubmitField

class GenerateForm(FlaskForm):
    def binary_generator(self, label_text, yes_text, no_text):
        return RadioField(label_text, choices=[(1, yes_text), (0, no_text)])

    submit = SubmitField('submit')

Flask app:

import GeneratorForm

form = GeneratorForm
form.radio_one = form.binary_generator('test label', 'yes', 'no')

render_template('file.html', form=form)

Jinja:

{{ form.radio_one.label }}
{{ form.radio_one(style="list-style: none") }}

The Jinja fails with: wtforms.fields.core.UnboundField object has no attribute label

So it looks like the class binary_generator function is working ok, but not constructing the form properly?

Dinko Pehar · Accepted Answer · 2019-09-25 08:24:01Z

3

Do you need that binary_generator method in GenerateForm ?

Your GenerateForm could look something like this:

from flask_wtf import FlaskForm
from wtforms import RadioField, SubmitField

class GenerateForm(FlaskForm):
    radio_fields = RadioField('', choices=[])
    submit = SubmitField('submit')

And in your flask application, you need to instantiate your form like this:

import GeneratorForm

form = GeneratorForm() # Instantiate it

form.radio_fields.label = 'Label Example'
form.radio_fields.choices = [('value_1', 'description'), ('value_2', 'description')] 

render_template('file.html', form=form)

To render your form in file.html:

<form method="post">
    {{ form.hidden_tag() }}
    {{ form.radio_fields.label }}
    {{ form.radio_fields(style='list-style: none') }}
    {{ form.submit }}
</form>

edited Sep 25, 2019 at 8:24

answered Dec 6, 2018 at 17:42

Dinko Pehar

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Comments

Attack68 · Accepted Answer · 2018-12-06 18:15:56Z

The base class FlaskForm is fairly particular about its construction. To define a dynamic form add the parameters after the base class has instantiated with super(). I.e.

class GenerateForm(FlaskForm):
    radio_fields = RadioField('', choices=[])
    submit = SubmitField('submit')

    def __init__(self, label, choices):
        super().__init__()
        self.radio_fields.choices = label
        self.radio_fields.choices = choices

Then you can instantiate the form with:

GenerateForm('My Label', [('val', 'desc'), ('val2', 'desc2')])]

You can also create a Form Factory in the following way:

def Form(n, *args):
    class FormGenerator(FlaskForm):
        submit = SubmitField('submit')

    for i in range(n):
        setattr(FormGenerator, RadioField(args[i][0], choices=args[i][1])

    return FormGenerator()

Then you can instantiate the form with:

Form(2, *(('rad1', [('v1', 'd1'), ('v2', 'd2')]), ('rad2', [('v1', 'd1'), ('v2', 'd2')])))

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