kms

Setting WTForms Selection Fields Dynamically

WTForms is a very useful tool for constructing web forms and operating on their data.

Setting selection fields dynamically from database content is not directly apparent, but they do provide one recipe to accomplish such functionality. I don’t mind this approach, but there are a few other options.

One approach that I’ve used is to provide a set_choices method:

class MyForm(Form):
    selection_field = SelectField()

    def set_choices(self):
        from models import Model
        self.selection_field.choices = query(Model).all()

You’d have to call the set_choices method after instantiating your form. This gives you some flexibility, but some redundant code.

Another option is to do this work in the __init__:

class MyForm(Form):
    ...
    def __init__(self):
        super(MyForm, self).__init__()

        from models import Model
        self.selection_field.choices = query(Model).all()

This allows you to use the filtered form without changing your external code.

Another approach would be to pass in the choices as a parameter to __init__:

class MyForm(Form):
    ...
    def __init__(self, selection_choices):
        super(MyForm, self).__init__()
        self.selection_field.choices = selection_choices