我正在使用 Flask-restful 并具有以下 API 类：

views.py

from datetime import date
from flask import jsonify
from flask.ext.restful import Resource, reqparse
from backend import db
from .models import User, Post, Comment, WorkExperience
from flask.ext.restful import fields, marshal
from backend.helpers import AuthRequiredResource, UserMixin

class CommentList(UserMixin, AuthRequiredResource):
    def __init__(self):
        self.fields = {
            'id': fields.Integer,
            'body': fields.String,
            'added_on': fields.DateTime

        }

        self.parser = reqparse.RequestParser()
        self.parser.add_argument('body')
        super(CommentList, self).__init__()

    def get(self, post_id):
        comments = Post.query.get_or_404(post_id).comments.all()
        # APPEARS THAT THE ERROR ARISES HERE
        return marshal(comments, fields)

    def post(self, post_id):
        args = self.parser.parse_args()
        user = self.get_user()
        c = Comment(post_id, args['body'], user.id)
        db.session.add(c)
        db.session.commit()

helper.py

from flask import request
from flask.ext.restful import Resource

from backend.models import User

class UserMixin(object):
    @staticmethod
    def get_user():
        user = User.query.filter_by(
            auth_token=request.headers.environ.get('HTTP_AUTHORIZATION')
        ).first()
        if user is None:
            return {'message': 'Invalid auth token'}, 401
        return user


class AuthRequiredResource(Resource):
    def dispatch_request(self, *args, **kwargs):

        if request.headers.environ.get('HTTP_AUTHORIZATION', None) is not None:
            return super(AuthRequiredResource, self).dispatch_request(*args,
                                                                      **kwargs)
        else:
            return {'message': 'Auth Token missing'}, 401

我面临着一个AttributeError: 'module' object has no attribute 'items'.

回溯是：

File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1836, in __call__
    return self.wsgi_app(environ, start_response)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1820, in wsgi_app
    response = self.make_response(self.handle_exception(e))
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 271, in error_router
    return original_handler(e)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1403, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 268, in error_router
    return self.handle_error(e)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1817, in wsgi_app
    response = self.full_dispatch_request()
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1477, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 271, in error_router
    return original_handler(e)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1381, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 268, in error_router
    return self.handle_error(e)
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1475, in full_dispatch_request
    rv = self.dispatch_request()
  File "/usr/local/lib/python2.7/dist-packages/flask/app.py", line 1461, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 477, in wrapper
    resp = resource(*args, **kwargs)
  File "/usr/local/lib/python2.7/dist-packages/flask/views.py", line 84, in view
    return self.dispatch_request(*args, **kwargs)
  File "/home/utkbansal/PycharmProjects/cv_backend/backend/helpers.py", line 12, in dispatch_request
    **kwargs)
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 587, in dispatch_request
    resp = meth(*args, **kwargs)
  File "/home/utkbansal/PycharmProjects/cv_backend/backend/views.py", line 130, in get
    return marshal(comments, fields)
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 635, in marshal
    if envelope else [marshal(d, fields) for d in data])
  File "/home/utkbansal/.virtualenvs/cv_backend/lib/python2.7/site-packages/flask_restful/__init__.py", line 639, in marshal
    for k, v in fields.items())
AttributeError: 'module' object has no attribute 'items'

看看类似的问题，这可能是循环依赖问题，但我无法弄清楚。所以我已经包含了上述两个文件的所有导入。

EDIT

使用 marshall 函数时，错误可能出现在 get 方法的返回行上。

fields是一个模块，在这里导入：

from flask.ext.restful import fields, marshal

因此，这双手marshal一个模块：

def get(self, post_id):
    comments = Post.query.get_or_404(post_id).comments.all()
    return marshal(comments, fields)

您可能想使用self.fields:

def get(self, post_id):
    comments = Post.query.get_or_404(post_id).comments.all()
    return marshal(comments, self.fields)