Passing a variable into a WTForms class

Question

I'm relatively inexperienced with Python and Flask, and am stuck trying to pass a variable to a WTForms class.

Here's what I have:

views.py

@app.route('/teacher/tasks/new') @login_required def new_hw_task(): classes = Class.query.filter_by(userid=current_user.userid).all() form = NewTaskForm(classes = classes) return render_template('/teacher/new_hw_task.html', form=form)

forms.py

class NewTaskForm(FlaskForm): classes = SelectMultipleField('Select classes to assign this homework to', choices = [("1", "Class 1"), ("2","Class 2")])

new_hw_task.html

<div class="form-group"> {{ form.classes.label }} {{ form.classes(class_="form-control selectpicker", placeholder=form.classes.description, title="Select at least one class to assign", show_tick=true)}} </div>

I want the classes variable (an instance of a Class class defined in models.py - yes, yes, I know how sloppy it is to have a class called 'Class') to be accessible in forms.py so that I can replace the choices in the SelectMultipleField with ones from classes. However, I can't find a way to pass it through (you can see that I've tried putting classes=classes into the parentheses after NewTaskForm).

Actually, my preferred way to do this would be to simply access current_user (the session-based object set by flask_login) from within forms.py, but I appear to be unable to do that either, even if I import current_user at the top of the file.

Is anybody able to explain to me where I'm going wrong here, please?

I suggest that you change the class name. Example: Users

Al Martins
– Al Martins

2024-05-26 13:03:04 +00:00
Commented May 26, 2024 at 13:03 — Al Martins
– Al Martins, Commented May 26, 2024 at 13:03

FallenWarrior · Accepted Answer · 2020-01-09 20:52:35Z

The WTForms documentation for SelectField explains how to pass variables into a form from a view. It's as simple as assigning a list of choices to form.field.choices. In turn, you remove the choices= keyword argument from the field constructor.

Adapted for your case, it would look like this.

@app.route('/teacher/tasks/new') @login_required def new_hw_task(): classes = Class.query.filter_by(userid=current_user.userid).all() form = NewTaskForm() form.classes.choices = classes return render_template('/teacher/new_hw_task.html', form=form)

Thanks a lot, I had search for a long time, this solution is very useful and simple!
Please explain "remove the choices=". How would forms.py look like?
Instead of SelectMultipleField('Select classes to assign this homework to', choices = [("1", "Class 1"), ("2","Class 2")]), use SelectMultipleField('Select classes to assign this homework to').

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