How to update foreign keys with new values properly? - flask

Question

I've been trying to build a web to check student attendance. I'm aiming to get a list of students of a classroom on a webpage
User class:
class User(db.Model, UserMixin):
id = db.Column(db.Integer, primary_key=True)
email = db.Column(db.String(80), unique=True, nullable=False)
name = db.Column(db.String(20), nullable=False)
password = db.Column(db.String(60), nullable=False)
image_file = db.Column(db.String(20), nullable=False, default='default.jpg')
occupation = db.Column(db.String(20), nullable=False)
year = db.Column(db.String(20), nullable=False)
classroom = db.Column(db.Integer, db.ForeignKey('classroom.id'))
posts = db.relationship('Post', backref='author', lazy=True)
def __repr__(self):
return f"User('{self.email}', '{self.name}', '{self.image_file}')"
Classroom class:
class Classroom(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(20), unique=True, nullable=False)
description = db.Column(db.String(80))
users = db.relationship('User', backref='user', lazy=True)
#classmethod
def get_classroom(cls):
classroom_list = Classroom.query.all()
return [(classroom.id, classroom.name) for classroom in classroom_list]
def __repr__(self):
return f"Classroom('{self.name}', '{self.description}')"
However, as classrooms were not created at first, no foreign keys were actually given to students in regard to their classrooms, then set as Null by default.
So, I was going to update the foreign keys by picking out one selection from a drop-down with HTML only but I could not figure out a proper solution and decided to try it with another method. A new form for that is now created and then it seems alright on a webpage. but the code isn't actually working well internally and posing some problems.
Form:
class SelectClassroomForm(FlaskForm):
name = StringField('Name')
year = StringField('Year')
classroom = SelectField('Classroom',
choices=Classroom.get_classroom(),
)
submit = SubmitField('Add')
Trying to update foreign keys:
#app.route("/students", methods=['GET', 'POST'])
#login_required
def students():
form = SelectClassroomForm()
students = User.query.filter(User.year != "I'm not a Student")
if form.validate_on_submit():
students.classroom = form.classroom.data[0]
db.session.commit()
flash('Successfully Added classroom info to students', 'success')
return redirect(url_for('students'))
else:
flash("something's wrong", 'danger')
return render_template('students.html', students=students, form=form)
I'm not sure whether it is the code above or HTML code down below that is stopping me from updating the keys..
HTML Code:
{% extends "layout.html" %}
{% block content %}
<h2>Student List</h2>
<div class="content-section">
<div class="table-responsive">
<table id="mytable" class="table table-bordered table-striped">
<thead>
<th> Name </th>
<th> Year </th>
<th> Classroom </th>
</thead>
<tbody>
{% for student in students %}
<tr>
<td> {{ student.name }} </td>
<td> {{ student.year }} </td>
<td>
<form method="POST" action="">
{{ form.classroom(class="form-control form-control-sm") }}
</form>
</td>
</tr>
{% endfor %}
</tbody>
</table>
</div>
<a class="btn btn-primary btn-sm mt-1 mb-1" href="{{ url_for('students') }}">Update</a>
</div>
{% endblock content %}
(sorry about the uncolored codes by the way I was trying to find out how to but failed on my own page)
Anyways, Here the webpage shows the list of students as it was supposed to be but when I click on the update button, that's when the problem turns up. How can I solve it and then successfully update students' info with new foreign keys? Any help will be much appreciated Thank you.