def read_form_field_string(model, form, field_name, transformation=None):
    """
    :param model: Model containing string field
    :param form: Form data from front-end
    :param field_name: Name of field shared by model and form
    :param transformation: Transformation of form data to perform before inserting into model
    :return: True if changes to model string field were made
    """
    field_changed = False
    if field_name in form.data:
        form_field_content = form.data.get(field_name)
        if transformation is not None:
            form_field_content = transformation(form_field_content)
        field_changed = getattr(model, field_name) != form_field_content
        setattr(model, field_name, form_field_content)
    return field_changed