这似乎应该很简单，但是我做错了。我想声明一个值，以便可以在顶部输入一次，然后在整个代码中使用它。
下面是一个简单的代码版本，但是它不起作用。运行它时没有任何结果，但是如果取出class NotificationRetrieveSerializer(serializers.ModelSerializer):
content_object = NotificationRelatedField(read_only=True)
class Meta:
model = Notification
fields = [
'id',
'created_at',
'is_read',
'type',
'content_object',
]
# override to_representation method
def to_representation(self, instance):
# python3 for `super` call
result = super().to_representation(instance)
# python2 for `super` call
# result = super(
# NotificationRetrieveSerializer, self
# ).to_representatio(instance)
# here you call your field's `to_representation` with current instance
# as the argument rather than as the `value` of the field.
result['content_object'] = content_object_field.to_representation(instance)
return result
class NotificationRelatedField(serializers.RelatedField):
# here `value` is now the `Notification` instance
def to_representation(self, value):
data = {}
# get the type and this field's value
type = value.type
content_object = value.content_object
return data
并手动进行设置，则会得到结果：
declare这是我尝试过的。
如上所述，我没有从查询中得到任何结果。它应该为我提供declare @orderno varchar
set @orderno = '739724'
SELECT ORDSIG.* FROM ordsig
WHERE ORDER_NO = @orderno
的数据，但事实并非如此。当我删除Order_NO并将其设置为常数Order_no = @orderno时，我得到一些数据结果。