烧瓶 wtforms-alchemy QuerySelectField ValueError：解压的值太多（预期为 2）

Question

i am trying to create sign up form using flask-wtf , and wtforms-alchemy on this form i try create selectfield, which the value is query from my models. but i'am always get this error:

 ValueError: too many values to unpack (expected 2)

this my code :

from flask_wtf import FlaskForm
from wtforms_sqlalchemy.fields import QuerySelectField

def choose_domicile():
    return Domicile.query

class RegisterForm(FlaskForm):
    name = StringField('Name', validators=[DataRequired()])
    domicile = QuerySelectField(u'Domicile', query_factory=choose_domicile)


@app.route('/signup', methods=['GET', 'POST'])
    def signup():
        form = RegisterFormView()
        try:
            if form.validate_on_submit():
                new_user = Data(name=form.name.data, domicile=form.domicile.data)
                db.session.add(new_user)
                db.session.commit()
                return "Success"
        except:
            return "Failed"

        return render_template('signup.html', form=form)

and this my signup.html :

{% block content %}
<div class="container">

  <form class="form-signin" method="POST" action="/signup">
    <h2 class="form-signin-heading">Sign Up</h2>
    {{ form.hidden_tag() }}
    {{ wtf.form_field(form.name) }}
    {{ form.domicile }}
    <button class="btn btn-lg btn-primary btn-block" type="submit">Sign Up</button>
  </form>

</div>
{% endblock %}

my package versions is flask-wtf==0.14.2 and wtforms-alchemy==0.16.7

i have try to follow this Why does Flask WTForms and WTForms-SQLAlchemy QuerySelectField produce too many values to unpack? , but i am still confused how to do that.

Answer 1

You can define a function as following which can be passed as a get_pk paramater.

def get_pk(obj):
    return str(obj)

and then do the following change

domicile = QuerySelectField(u'Domicile', query_factory=choose_domicile, get_pk=get_pk)

I am assuming that you have define __str__ in model class else return pk in get_pk