Pass a variable to a Flask WTForm

Question

I want to do a query select field with a default value that is passed in from the route. I can't figure out how to pass a variable from the View to the Form class

class transactionsForm(Form):

loan_id = QuerySelectField('trans_id', validators=[Required()], get_label='name',
                           query_factory=lambda: trans.query.filter_by(trans_id=[MY VARIABLE]).all())

Answer 1

This is from the QuerySelectField documentation:

The query property on the field can be set from within a view to assign a query per-instance to the field. If the property is not set, the query_factory callable passed to the field constructor will be called to obtain a query.

What this means is that you define your form with the query:

class transactionsForm(Form):
    loan_id = QuerySelectField('trans_id', validators=[Required()], get_label='name')

And then in your view function you assign the query once you have an instance:

def viewFunction(my_variable):
    form = transactionsForm()
    my_query = trans.query.filter_by(trans_id=my_variable)
    form.loan_id.query = my_query
    if form.validate_on_submit():
        # ...

Answer 2

See my other answer here: https://stackoverflow.com/a/17638018/880326.

So it looks like:

form = transactionsForm(request.form, loan_id='default')