python - Django annotate()错误AttributeError:'CharField'对象没有属性'resolve_expression'

您好，我想将更多字段连接到django中，但即使是以下简单代码：

    Project.objects.annotate(
        companyname=Concat('company__name',Value('ahoj')),output_field=CharField()
    )

给我一个错误：

AttributeError: 'CharField' object has no attribute 'resolve_expression'

回溯：

  File "/root/MUP/djangoenv/lib/python3.4/site-packages/django/db/models/manager.py", line 122, in manager_method
    return getattr(self.get_queryset(), name)(*args, **kwargs)
  File "/root/MUP/djangoenv/lib/python3.4/site-packages/django/db/models/query.py", line 908, in annotate
    clone.query.add_annotation(annotation, alias, is_summary=False)
  File "/root/MUP/djangoenv/lib/python3.4/site-packages/django/db/models/sql/query.py", line 986, in add_annotation
    annotation = annotation.resolve_expression(self, allow_joins=True, reuse=None,
AttributeError: 'CharField' object has no attribute 'resolve_expression'

最佳答案

右括号的位置不对。output_field是Contcat的参数，而不是annotate的参数。应该是：

Project.objects.annotate(
    companyname=Concat('company__name', Value('ahoj'), output_field=CharField()),
)

关于python - Django annotate()错误AttributeError:'CharField'对象没有属性'resolve_expression'，我们在Stack Overflow上找到一个类似的问题：https://stackoverflow.com/questions/35289273/