Flask/WTForms/QuerySelectField - render QuerySelectField with a choice selected based on existing database value

Question

I am building a simple CMS that includes a profile management page. On this profile page, along with other fields, there exists a dropdown list, which I generate from a table 'parks' using the wtforms extension's QuerySelectField:

from wtforms.ext.sqlalchemy.fields import QuerySelectField

The rest of the fields on the profile page are populated by the 'user' table.

Let assume that a user has logged in, and that their record in the 'user' table is already populated. Among the fields in the 'user' table is a foreign key for a value from the 'parks' table: 'park_id'.

When a logged in user navigates to their profile page, I would like to display the selection in the dropdown that corresponds to this user's park_id foreign key value.

Note that Flask/Python et al is very new to me. Also, I am using Flask-Security and the User model below is based off their examples. Perhaps I need to build another relationship with users/parks?

Displaying a user's saved profile information, including that which might appear in a dropdown list to be made available for editing seems very basic to me. I fear I'm missing something fundamental. So far, other similar questions/answers on SO and elsewhere seem wildly confusing to me.

My User Model:

# Define models
roles_users = db.Table('roles_users',
        db.Column('user_id', db.Integer(), db.ForeignKey('user.id')),
        db.Column('role_id', db.Integer(), db.ForeignKey('role.id')))

class Role(db.Model, RoleMixin):
    id = db.Column(db.Integer(), primary_key=True)
    name = db.Column(db.String(80), unique=True)
    description = db.Column(db.String(255))

class User(db.Model, UserMixin):
    id = db.Column(db.Integer, primary_key=True)
    email = db.Column(db.String(255), unique=True)
    password = db.Column(db.String(255))
    active = db.Column(db.Boolean())
    confirmed_at = db.Column(db.DateTime())
    roles = db.relationship('Role', secondary=roles_users,
                            backref=db.backref('users', lazy='dynamic'))
    park_id = db.Column(db.Integer)
    weather_zip = db.Column(db.String(255))
    flickr_api_key = db.Column(db.String(255))
    flickr_api_secret = db.Column(db.String(255))
    flickr_user_id = db.Column(db.String(255))
    flickr_photo_set_id = db.Column(db.String(255))

My Parks Model:

class Parks(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    park = db.Column(db.String(255))

My Profile Form (with query_factory thing)

def get_parks():
    return Parks.query

class ProfileForm(Form):
    id = HiddenField()
    email = HiddenField()
    park_id = QuerySelectField('Park',[validators.InputRequired(u'Please select a park')], default=19, query_factory=get_parks, get_label='park', allow_blank=True)
    weather_zip = StringField('Zip Code',[validators.Length(min=5, max=5, message=u'Zip must contain 5 numbers'), validators.InputRequired(u'please enter a 5-digit zip code')])
    flickr_api_key = StringField('Flickr API Key', [validators.InputRequired(u'Please supply a Flickr API key')])
    flickr_api_secret = StringField('Flickr API Secret', [validators.InputRequired(u'Please supply a Flickr API secret')])
    flickr_user_id = StringField('Flickr User ID', [validators.InputRequired(u'Please supply a Flickr user id')])
    flickr_set_id = StringField('Flickr Set ID', [validators.InputRequired(u'Please supply a Flickr set id')])

My profile_page view:

@app.route('/profile/<id>', methods=["GET","POST"])
@login_required
def profile_page(id):

    id = id
    current_user = User.query.filter_by(id=id).first()

    form = ProfileForm(obj=current_user)

    return render_template("profile.html", form=form)

My template's form:

    {% from "_formhelpers.html" import render_field %}
    <form method=post action="/profile">
      <dl>
        {{ form.id(value=current_user.id) }}
        {{ form.email(value=current_user.email) }}
        {{ render_field(form.park_id) }}
        {{ render_field(form.weather_zip) }}
        {{ render_field(form.flickr_api_key) }}
        {{ render_field(form.flickr_api_secret) }}
        {{ render_field(form.flickr_user_id) }}
        {{ render_field(form.flickr_set_id) }}
      </dl>
      <p><input type=submit value=Register>
    </form>

A macro to render the fields (might be relevant?):

{% macro render_field(field) %}
    <dt>{{ field.label }}
    <dd>{{ field(**kwargs) |safe }}
    {% if field.errors %}
        <ul class=errors>
        {% for error in field.errors %}
            <li>{{ error }}</li>
        {% endfor %}
        </ul>
    {% endif %}
    </dd>
{% endmacro %}

Thanks for any help on all of this.

Answer 1

After drinking a couple beers and starring at this post: SQLAlchemy/WTForms: set default selected value for QuerySelectField until my eyes crossed, I discovered that I needed to pass a result object from a query to my parks table filtered by the current user's id.

A special detail is that I had to manually assign each field value (aside from the QuerySelectField, parks) from the current user's query result. This is because, in my case, simply passing the current_user result to the "obj=" arg would override my QuerySelectField keyword (in my case "park_id") because the "obj=current_user" assignment already contains its own instance of the park_id parameter, albeit one that doesn't work for displaying a default selection in my drop down.

So... The fix was to update my profile_page view function as follows:

@app.route('/profile/<id>', methods=["GET","POST"])
@login_required
def profile_page(id):

    id = id
    current_user = User.query.filter_by(id=id).first()
    park = Parks.query.filter_by(id=current_user.park_id).first()
    form = ProfileForm(park_id=park, # this is the main thing
                       weather_zip=current_user.weather_zip,
                       flickr_api_key=current_user.flickr_api_key,
                       flickr_api_secret=current_user.flickr_api_secret,
                       flickr_user_id=current_user.flickr_user_id,
                       flickr_photo_set_id=current_user.flickr_photo_set_id)

    return render_template("profile.html", form=form)