CODEWITHSUNDEEP
pythonflaskjinja2
Brian
Brian

Reputation: 25

Jinja2 templates If condition not working correctly

I have an if-statement in a Jinja2 template in complete.html, but it doesn't run the right code regardless if the if-condition is True or False.

I call a redirect url to another view function which then renders it, carrying the variable that determines the condition of the if-loop. I printed out the condition and it's correct, but the if-loop doesn't run the correct code. Am I missing something that is causing the if-statement to not work correctly.

My code:

view.py

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

    if form.validate_on_submit():
        course_name = form.cname.data.upper()
        course_id = form.cid.data
        course_sec = form.sec.data.upper()
        email = form.email.data.lower()
        reserved = form.reserved.data

        result = checkCourse(course_name, course_id, course_sec)
        if result is not None:
            flash('Unable to find course')
        else:
            known = False
            course = Course.query.filter_by(cname=course_name, cid=course_id, sec=course_sec).first()
            if course is None:
                course = Course(cname=course_name, cid=course_id, sec=course_sec)
                db.session.add(course)
                db.session.flush()
                user = User(email=email, course_id=course.id, reserved=reserved)
                db.session.add(user)
            else:
                ckey = course.id
                result = checkUser(email, ckey, reserved)
                if result != None:
                    known = True
                else:
                    user = User(email=email, course_id=ckey, reserved=reserved)
                    db.session.add(user)
            db.session.commit()
            return redirect(url_for('complete', known=known))
    return render_template('home.html', form=form)

@app.route('/complete')
def complete():
    known = request.args.get('known', type=string)
    app.logger.debug(known)
    return render_template('complete.html', known=known)

Templates:

base.html

{% extends "bootstrap/base.html" %}

{% block title %}UBC Course Alert{% endblock %}

{% block styles %}
{{super()}}
<link rel="stylesheet"
      href="{{url_for('.static', filename='home.css')}}">
{% endblock %}

{% block content %}
<div class="jumbotron">
    <div class="container">
        {% block page_content %}{% endblock %}
    </div>
</div>
{% endblock %}

complete.html

{% extends "base.html" %}
{% import "bootstrap/wtf.html" as wtf %}

{% block page_content %}

<p>
{% if known %}
  You already added this course. You'll receive a email as soon as there's space :)
{% else %}
  Thanks for registering your course, you'll receive a email as soon as there's space!
{% endif %}
</p>

{% endblock %}

Upvotes: 2

Views: 4088

Answers (1)

Martijn Pieters
Martijn Pieters

Reputation: 1121236

You converted the variable known to a string; it'll contain either the string value 'True' or 'False'. These are not boolean values, but rather strings of either 4 or 5 characters long. Both strings then are seen as true values, as they are non-empty.

You'll either have to translate the string to a boolean, or leave the known value empty to indicate a false value.

Converting back to boolean would be as easy as:

known = request.args.get('known', type=string) == 'True'

while using an empty value for false would look like this:

return redirect(url_for('complete', known='1' if known else ''))

and

known = request.args.get('known', default='', type=bool)

Upvotes: 1

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