如何在 Flask 应用程序中正确更新博客文章上的标签？

Question

I have a taking notes system where each note can be associate with one or many tags.

Here is my model for that part:

tags = db.Table('tags',
                db.Column('tag_id', db.Integer, db.ForeignKey(
                    'tag.id'), primary_key=True),
                db.Column('notes_id', db.Integer, db.ForeignKey(
                    'notes.id'), primary_key=True)
                )


class Notes(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    # ...
    tags = db.relationship('Tag', secondary=tags, lazy='subquery',
                           backref=db.backref('notes', lazy=True))


class Tag(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(50), nullable=None)

    def __init__(self, name):
        self.name = name

I would like to remove the tags that are no longer associated with my note when I update this note. How can I do that?

For instance, it's what I have:

@bp.route('/update/<int:id>', methods=['GET', 'POST'])
@login_required
def update(id):
    note = Notes.query.get_or_404(id)

    tags = []
    for e in note.tags:
        tag = Tag.query.get_or_404(e.id)
        tags.append(tag.name)
    tags = ', '.join(tags)

    if request.method == 'POST':
        note.title = request.form.get('title')
        note.content = request.form.get('content')
        note.updated_at = datetime.now()

        # Get a tags list from an input and convert it to string
        tags = request.form.get('tags').split(', ')

        if tags:
            for tag in tags:
                tag_exists = Tag.query.filter_by(name=tag).first()
                if not tag_exists:
                    new_tag = Task(tag)
                    db.session.add(new_tag)
                    note.tags.append(new_tag)
                else:
                    db.session.add(tag_exists)
                    note.tags.append(tag_exists)

        # Want to check if I have to delete tags associations here..

        db.session.add(note)
        db.session.commit()
        return redirect(url_for('notes.index'))
    else:
        if note.owner_id == int(current_user.get_id()):
            return render_template('notes/update.html', note=note, tags=tags)
        else:
            flash("You can't update a page which is not yours", "error")
            return redirect(url_for('notes.index'))

I know my code is a bit dirty but it's my first real app with Flask, I do my best

Thank you for help

Answer 1

Here is an example, hope this helps

# find note which you want change
note = Notes.query.get(3)
# find tag which you want delete
tag = note.tags[0]
note.tags.remove(tag)
db.session.add(note)
db.session.commit()