如何使用Django Rest Framework序列化程序一次调用同一方法来设置多个字段？这就是我现在要做的,但这显然两次调用了该方法.如何限制它只能被调用一次？

class MyModel(models.Model):
    def GetTwoValues(self):
        foo = []
        bar = []

        # expensive operation

        return foo, bar

class MyModelSerializer(serializers.HyperlinkedModelSerializer):
    foo = serializers.SerializerMethodField()
    bar = serializers.SerializerMethodField()

    def get_foo(self, obj):
        foo, _ = obj.GetTwoValues()
        return foo

    def get_bar(self, obj):
        _, bar = obj.GetTwoValues()
        return bar

    class Meta:
        model = MyModel
        fields = ('FirstValue', 'SecondValue',)

解决方法:

有几种选择：

1)存储值,以便仅调用一次昂贵的方法.例如.：

def _get_two_values(self, obj):
    if not hasattr(self, '_two_values'):
        self._two_values = obj.GetTwoValues()
    return self._two_values

def get_foo(self, obj):
    foo, _ = self._get_two_values(obj)
    return foo

def get_bar(self, obj):
    _, bar = self._get_two_values(obj)
    return bar

2)从序列化器中删除两个字段,并在序列化器的to_representation方法中分配两个值.例如.：

def to_representation(self, obj):
    data = super().to_representation(obj)
    foo, bar = obj.GetTwoValues()
    data['foo'] = foo
    data['bar'] = bar
    return data