django-fsm中的状态转换错误，并将当前状态重置为默认值

Question

我有一个订单模型，它有一个字段status，它有选项-> NEW (默认)，PENDING(PDG)，DISPATCHED(DSP)，COMPLETED(CMP)，CLD(CLD)

models.py

class Order(Address, TimeStampedUUIDModel):

    status = FSMField(
        max_length=25,
        choices=constants.STATUS_CHOICES,
        default=constants.NEW,
    )

    @transition(field=status, source=constants.NEW, target=constants.PDG)
    def to_pending(self):
        self.status = constants.PDG


    @transition(field=status, source=constants.PDG, target=constants.DSP)
    def to_dispatched(self):
        self.status = constants.DSP


    @transition(field=status, source=constants.DSP, target=constants.CMP)
    def to_completed(self):
        self.status = constants.CMP


    @transition(
        field=status,
        source=[constants.NEW, constants.PDG, constants.DSP],
        target=constants.CLD,
    )
    def to_cancel(self):
        self.status = constants.CLD

serializers.py

class OrderSerializer(serializers.ModelSerializer):
    class Meta:
        model = models.Order
        fields = "__all__"
        read_only_fields = [--all fields except status--]

    def update(self, instance, validated_data):
        status = validated_data.pop("status", None)
        agent =  self.context['request'].user
        instance = services.status_function(status, instance, agent)
        return instance

在下面的服务文件中，我同时尝试创建一个order活动对象来跟踪Order对象中的更改。services.py

def status_function(status, instance, agent):
    if status is not None:
        switcher = {
            constants.PDG : instance.to_pending,
            constants.DSP : instance.to_dispatched,
            constants.CMP : instance.to_completed,
            constants.CLD : instance.to_cancel
        }
        func = switcher.get(status, None)
        try:
            func()
            models.OrderActivity.objects.create(
                event_name=status,
                order = instance,
                event = f"Order {status}",
                agent = agent,
                time = instance.modified_at
            )
        except TransitionNotAllowed :
            print("Exception Caught")
            raise exceptions.BadRequest([{"error": "Transition not allowed"}])

    return instance

constants.py

from extended_choices import Choices

## Order Status
NEW, NEW_ = "NEW", "NEW"
PDG, PDG_ = "PDG", "PENDING"
DSP, DSP_ = "DSP", "DISPATCHED"
CMP, CMP_ = "CMP", "COMPLETED"
CLD, CLD_ = "CLD", "CANCELLED"

STATUS_CHOICES = ( 
    (NEW, NEW_), 
    (PDG, PDG_), 
    (DSP, DSP_), 
    (CMP, CMP_),
    (CLD, CLD_),
)

我的问题是，除了NEW Order PDG、NEW Order CLD和PDG -> CLD之外的其他转换都会引发异常，并且还会将->对象的状态恢复为NEW，这是不应该发生的。提前感谢！

Answer 1

从每个转移函数中删除赋值

将每个转换函数更改为：

    def to_completed(self):
            return

因为状态是通过调用函数本身改变的。但不会在数据库中更改。所以我们只需要保存实例本身。services.py put中的func()下面

instance.save()