1

我有以下 Python 类和 Marshmallow 模式定义：

from marshmallow import Schema, fields, post_load

class Author:
    def __init__(self, id, name):
        self.id = id
        self.name = name


class Book:
    def __init__(self, id, author, name):
        self.id = id
        assert isinstance(author, Author)
        self.author = author
        self.name = name


class Library:
    def __init__(self, authors, books):
        self.authors = authors
        self.books = books


class AuthorSchema(Schema):
    id = fields.Int()
    name = fields.Str()

    @post_load
    def make_obj(self, data):
        return Author(**data)


class BookSchema(Schema):
    id = fields.Int()
    author_id = fields.Method('get_id', 'get_author', attribute="author")
    name = fields.Str()

    @post_load
    def make_obj(self, data):
        return Book(**data)

    def get_id(self, obj):
        return obj.author.id

    def get_author(self, value):
        return [a for a in authors if a.id == value][0]


class LibrarySchema(Schema):
    authors = fields.List(fields.Nested(AuthorSchema()))
    books = fields.List(fields.Nested(BookSchema()))

    @post_load
    def make_obj(self, data):
        return Library(**data)

    # preserve ordering of fields
    class Meta:
        ordered = True


def test_author_referencing():
    author1 = Author(1, "Astrid Lindgren")
    author2 = Author(2, "Tove Jansson")

    book1 = Book(11, author1, "The Brothers Lionheart")
    book2 = Book(12, author2, "Comet in Moominland")

    library = Library(authors=[author1, author2], books=[book1, book2])

    schema = LibrarySchema(strict=True)

    library_dict = schema.dump(library).data
    library2 = schema.load(library_dict).data

正如示例希望说明的那样，我希望有一个数据模型，其中书籍对象包含对作者的引用（而不仅仅是作者 ID），但会被序列化为作者 ID。

显然，序列化不是问题，但是在反序列化时，我需要访问作者列表中已经反序列化的内容。我不知道如何用棉花糖做到这一点。甚至可能吗？当然，在这种情况下，我可以Book用数字作者 ID 实例化对象并执行@post_load操作LibrarySchema以将作者 ID 替换为引用，但这对我来说感觉又脏又笨重。请帮忙。:-)

4

1 回答 1

0

在 post_load 中链接数据正是你应该做的。

于 2016-11-30T23:57:50.453 回答