Modals for Flask

Use forms in Bootstrap modals with Flask.

Description

Plain forms can be boring. Using them in modals is possible, but requires JavaScript. Normal form submission in modals is problematic.

This Flask extension eases the process of using forms in Bootstrap modals. Bootstrap versions 4 and 5 are supported. No JavaScript coding is required on your part. You can code in pure Python - flashing messages and rendering templates.

Installation

pip install Flask-Modals

Setup

1. Import the Modal class and instantiate it in your app.py file.

   from flask_modals import Modal
   
   app = Flask(__name__)
   modal = Modal(app)

   You will also need a secret key in the app config (not shown).
   

2. Alternatively if you are using the application factory pattern:

   from flask_modals import Modal
   
   modal = Modal()
   
   def create_app():
       app = Flask(__name__)
       modal.init_app(app)

   
   

3. Include the following in the head tag of your base template.

   {{ modals() }}

   
   

4. Include the following in the modal body.

   <div class="modal-body">
   {{ modal_messages() }}
   <form method="post">
   ...

Basic usage

You only need to import the function render_template_modal in your routes.py file. Use it instead of render_template in the route handler for the page with the modal form. It takes an extra argument - modal (the modal id with a default of modal-form).
The extension works by submitting the modal form twice - first via ajax and then, if all validations pass, normally. When submiited via ajax, it passes a field '_ajax' with the form, which can be used as shown below.

Example route handler:

from flask_modals import render_template_modal

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

    ajax = '_ajax' in request.form  # Add this line
    form = LoginForm()
    if form.validate_on_submit():
        if form.username.data != 'test' or form.password.data != 'pass':
            flash('Invalid username or password', 'danger')
            return redirect(url_for('index'))

        if ajax:        # Add these
            return ''   # two lines
        login_user(user, remember=form.remember_me.data)

        flash('You have logged in!', 'success')
        return redirect(url_for('home'))

    # Add this line
    return render_template_modal('index.html', form=form)

Other usage

If you want to render a template and not redirect:

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

    ajax = '_ajax' in request.form
    form = LoginForm()
    if form.validate_on_submit():
        if form.username.data != 'test' or form.password.data != 'pass':
            flash('Invalid username or password', 'danger')
            return render_template_modal('index.html', form=form)

        if ajax:
            return ''
        login_user(user, remember=form.remember_me.data)

        flash('You have logged in!', 'success')
        return render_template_modal('index.html', form=form)

    return render_template_modal('index.html', form=form)

If the above looks verbose, you can use the response decorator and return a context dictionary, like so:

from flask_modals import response

@app.route('/', methods=['GET', 'POST'])
@response('index.html')
def index():
    ...
    ...
    return {'form': form}

Note

1. See the examples folder in the repo for more details.

2. The extension loads the NProgress js library to display a progress bar during form submission.