仅加载_，仅转储嵌套字段

Question

marshmallow sqlalchemy中有没有方法在序列化/反序列化zng Bar时为嵌套（foos）指定只加载或只转储字段吗？在

class FooSchema(BaseSchema):
    class Meta(BaseSchema.Meta):
        model = Foo
        fields = ('id', 'name', 'date', 'clients')


class BarSchema(BaseSchema):
    class Meta(BaseSchema.Meta):
        model = Bar
        fields('id',)
    foos = Nested(FooSchema, many=True, only=('id', 'name'))
# is there a way to add to foos field something like load_only=('id',)
# without changing FooSchema?

Answer 1

我建议不要在Nested关系的定义中指定only。使用exclude来防止循环引用，并在每次序列化时显式指定要only的字段。在

另外，您通常不需要指定fields-marshmallow-sqlalchemy为大多数字段免费提供了这个选项。下面是我如何重构上述内容：

class FooSchema(BaseSchema):
    bar = Nested('myproject.schemas.bar.BarSchema', exclude=('foos',))
    class Meta(BaseSchema.Meta):
        model = Foo
        dump_only = ('id',)


class BarSchema(BaseSchema):
    class Meta(BaseSchema.Meta):
        model = Bar
        dump_only = ('id',)
    # don't specify `only` here:
    foos = Nested(FooSchema, many=True, exclude=('bar',))