創建model_form引發'SQLAlchemy'對象沒有屬性'查詢'錯誤

Question

我正在使用WTForms'model_form創建基於Flask-SQLAlchemy模型的表單。如果模型上有外鍵，我會得到AttributeError: 'SQLAlchemy' object has no attribute 'query'。爲什麼我得到這個錯誤，我該如何解決它？

from wtforms.ext.sqlalchemy.orm import model_form 

class BREADView(MethodView):   
    def __init__(self,endpoint_param,model_param,exclude=None): 
     self.endpoint = endpoint_param; 
     self.model = model_param;   
     self.path = url_for('.%s' % self.endpoint) 
     self.DetailForm = model_form(self.model, db_session=db, base_class=Form) 
     self.DetailForm.submit = SubmitField('Submit') 

    def get(self, obj_id='', operation=''): 
     if operation == 'new':   
      new_form = self.DetailForm(request.form)    
      return render_template(
       self.detail_template, 
       form=new_form, 
      ) 

Traceback (most recent call last): 
    File "/bin/user_wsgi_wrapper.py", line 130, in __call__ 
    self.error_log_file.logger.exception("Error running WSGI application") 
    File "/usr/lib/python3.4/logging/__init__.py", line 1296, in exception 
    self.error(msg, *args, **kwargs) 
    File "/usr/lib/python3.4/logging/__init__.py", line 1289, in error 
    self._log(ERROR, msg, args, **kwargs) 
    File "/usr/lib/python3.4/logging/__init__.py", line 1395, in _log 
    self.handle(record) 
    File "/usr/lib/python3.4/logging/__init__.py", line 1404, in handle 
    if (not self.disabled) and self.filter(record): 
    File "/usr/lib/python3.4/logging/__init__.py", line 692, in filter 
    for f in self.filters: 
    File "/bin/user_wsgi_wrapper.py", line 122, in __call__ 
    app_iterator = self.app(environ, start_response) 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1836, in __call__ 
    return self.wsgi_app(environ, start_response) 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1820, in wsgi_app 
    response = self.make_response(self.handle_exception(e)) 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1403, in handle_exception 
    reraise(exc_type, exc_value, tb) 
    File "/usr/local/lib/python3.4/dist-packages/flask/_compat.py", line 33, in reraise 
    raise value 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1817, in wsgi_app 
    response = self.full_dispatch_request() 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1477, in full_dispatch_request 
    rv = self.handle_user_exception(e) 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1381, in handle_user_exception 
    reraise(exc_type, exc_value, tb) 
    File "/usr/local/lib/python3.4/dist-packages/flask/_compat.py", line 33, in reraise 
    raise value 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1475, in full_dispatch_request 
    rv = self.dispatch_request() 
    File "/usr/local/lib/python3.4/dist-packages/flask/app.py", line 1461, in dispatch_request 
    return self.view_functions[rule.endpoint](**req.view_args) 
    File "/usr/local/lib/python3.4/dist-packages/flask/views.py", line 84, in view 
    return self.dispatch_request(*args, **kwargs) 
    File "/usr/local/lib/python3.4/dist-packages/flask/views.py", line 149, in dispatch_request 
    return meth(*args, **kwargs) 
    File "/home/severedblue/mysite/app/uct/views.py", line 53, in get 
    endpoint=self.endpoint, 
    File "/usr/local/lib/python3.4/dist-packages/flask/templating.py", line 128, in render_template 
    context, ctx.app) 
    File "/usr/local/lib/python3.4/dist-packages/flask/templating.py", line 110, in _render 
    rv = template.render(context) 
    File "/usr/local/lib/python3.4/dist-packages/jinja2/environment.py", line 969, in render 
    return self.environment.handle_exception(exc_info, True) 
    File "/usr/local/lib/python3.4/dist-packages/jinja2/environment.py", line 742, in handle_exception 
    reraise(exc_type, exc_value, tb) 
    File "/usr/local/lib/python3.4/dist-packages/jinja2/_compat.py", line 36, in reraise 
    raise value.with_traceback(tb) 
    File "/home/severedblue/mysite/app/templates/form.html", line 2, in <module> 
    {% import "bootstrap/wtf.html" as wtf %} 
    File "/home/severedblue/mysite/app/templates/base.html", line 1, in <module> 
    {% extends "bootstrap/base.html" %} 
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 1, in <module> 
    {% block doc -%} 
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 4, in <module> 
    {%- block html %} 
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 20, in <module> 
    {% block body -%} 
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/base.html", line 23, in <module> 
    {% block content -%} 
    File "/home/severedblue/mysite/app/templates/base.html", line 23, in <module> 
    {% block page_content %}{% endblock %} 
    File "/home/severedblue/mysite/app/templates/form.html", line 11, in <module> 
    {{ wtf.quick_form(form) }} 
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/wtf.html", line 195, in <module> 
    {{ form_field(field, 
    File "/home/severedblue/.local/lib/python3.4/site-packages/flask_bootstrap/templates/bootstrap/wtf.html", line 116, in <module> 
    {{field(class="form-control", **kwargs)|safe}} 
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/fields/core.py", line 149, in __call__ 
    return self.meta.render_field(self, kwargs) 
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/meta.py", line 53, in render_field 
    return field.widget(field, **render_kw) 
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/widgets/core.py", line 280, in __call__ 
    for val, label, selected in field.iter_choices(): 
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/ext/sqlalchemy/fields.py", line 107, in iter_choices 
    for pk, obj in self._get_object_list(): 
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/ext/sqlalchemy/fields.py", line 98, in _get_object_list 
    query = self.query or self.query_factory() 
    File "/home/severedblue/.local/lib/python3.4/site-packages/wtforms/ext/sqlalchemy/orm.py", line 121, in <lambda> 
    'query_factory': lambda: db_session.query(foreign_model).all() 
AttributeError: 'SQLAlchemy' object has no attribute 'query' 

Answer 1

你指出model_form在SQLAlchemy的擴展對象，而不是會話提供。改爲使用db.session。

self.DetailForm = model_form(self.model, db_session=db.session, base_class=Form)