WTForms populate_obj advantage

populate_obj_in_wtforms.py

##Complex Models:

class Profile(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String(100))
    reports = db.relationship(
        'Report', backref='profile_of_report', lazy='dynamic')

class Report(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    profile_id = db.Column(db.Integer, db.ForeignKey(Profile.id))
    disease_name = db.Column(db.String(50))
    reported_date = db.Column(db.DateTime(), default=datetime.now())


##The form:


class ProfileForm(Form):
    name = StringField('Name', validators=[validators.Required()])
    reports = FieldList(FormField(ReportForm), min_entries=2)

class ReportForm(Form):
    disease_name = StringField('Disease Name')
    reported_date = DateField('Reported Date', default=date.today())


##The view:

def profile_page():
    form = ProfileForm()
    if request.method == 'POST':
        if form.validate_on_submit():
            profile = Profile()
            for _ in form.reports #we create the same number of object which we need to populate.
                profile.reports.append(Report())
            form.populate_obj(profile)
            db.session.add(profile)
            db.session.commit()
    return render_template('profile_page.html', form=form)

Have problems with wtforms populate_obj?
Even I had few and this hetsch gist helped me to understand the working. Also this wtform google mailing list support of the same gist helped me realize what was I doing wrong.
I also followed the second link and this statement For that to work, the items must already exist in the list of the original object. In your case, your 'plugins' don't exist in your 'post' object, thus they cannot be updated gave me a better idea. check this out. This new idea was inspired from the gist but has no relation to the problem mentioned in hetsch gist.

Basically populate_obj of the wtfform helps us to dynamicallly populate our model data. But there is a small issue with the FieldList and FormField, the model objects should exist.

Check this out.
Well it was true that you need an object to exist to pass a value, and now you can see how easy data population is with Wtfforms.

Thanks. It seems to work fine. Also, Have you tried https://github.com/kvesteri/wtforms-alchemy ?