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flask - 如何使模型烧瓶棉花糖_sqlalchemy反序列化相关对象

问题描述

我有这个代码：

import sqlalchemy as sa
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import scoped_session, sessionmaker, relationship, backref

engine = sa.create_engine("sqlite:///:memory:")
session = scoped_session(sessionmaker(bind=engine))
Base = declarative_base()


class Author(Base):
    __tablename__ = "authors"
    id = sa.Column(sa.Integer, primary_key=True)
    name = sa.Column(sa.String, nullable=False)
    books = relationship("Book", backref=backref("author", lazy="joined"),
                         foreign_keys="Book.author_id", lazy="dynamic")

    def __repr__(self):
        return "<Author(name={self.name!r})>".format(self=self)


class Book(Base):
    __tablename__ = "books"
    id = sa.Column(sa.Integer, primary_key=True)
    title = sa.Column(sa.String)
    author_id = sa.Column(sa.Integer, sa.ForeignKey("authors.id"))


Base.metadata.create_all(engine)


from marshmallow_sqlalchemy import SQLAlchemySchema, auto_field, SQLAlchemyAutoSchema


class AuthorSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Author
        load_instance = True  # Optional: deserialize to model instances
        # dump_only = ("id",)
        include_fk = True


class BookSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Book
        load_instance = True
        # dump_only = ("id",)
        include_fk = True


author = Author(name="Chuck Paluhniuk")
author_schema = AuthorSchema()
book = Book(title="Fight Club", author=author)
book_schema = BookSchema()
session.add(author)
session.add(book)
session.commit()

dump_data_author = author_schema.dump(author)
print(dump_data_author)

dump_data_book = book_schema.dump(book)
print(dump_data_book)

当我运行它打印的代码时：

{'id': 1, 'name': 'Chuck Paluhniuk'}
{'id': 1, 'author_id': 1, 'title': 'Fight Club'}

我想更改代码以使其打印：

{'id': 1, 'name': 'Chuck Paluhniuk', 'books': [{'id': 1, 'author_id': 1, 'title': 'Fight Club'}]}
{'id': 1, 'author_id': 1, 'title': 'Fight Club'}

我该怎么做？

我想控制反序列化相关对象。

我也对元数据中的一些其他设置感到好奇，例如 load_only 和 dump_only 和 excelude 等。

标签： flaskflask-sqlalchemyflask-restfulflask-marshmallow

解决方案

在我看来，有必要定义嵌套字段以便以这种方式在输出中包含关系。您可以定义自动包含关系，但这仅适用于主键。为了不使用字段的覆盖，我没有包含关系。

from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from marshmallow_sqlalchemy import SQLAlchemyAutoSchema
from flask_marshmallow import Marshmallow

app = Flask(__name__)
db = SQLAlchemy(app)
ma = Marshmallow(app)

class Author(db.Model):
    __tablename__ = "authors"
    id = db.Column(db.Integer, primary_key=True)
    name = db.Column(db.String, nullable=False)
    books = db.relationship("Book",
        backref=db.backref("author", lazy="joined"),
        foreign_keys="Book.author_id",
        lazy="dynamic"
    )

class Book(db.Model):
    __tablename__ = "books"
    id = db.Column(db.Integer, primary_key=True)
    title = db.Column(db.String)
    author_id = db.Column(db.Integer, db.ForeignKey("authors.id"))

class BookSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Book
        include_fk = True
        load_instance = True
        sqla_session = db.session

class AuthorSchema(SQLAlchemyAutoSchema):
    class Meta:
        model = Author
        load_instance = True
        # include_relationships = True # See below
        sqla_session = db.session
    books = ma.Nested(BookSchema, many=True)


with app.app_context():
    db.drop_all()
    db.create_all()

    author = Author(name="Chuck Paluhniuk")
    book = Book(title="Fight Club", author=author)
    db.session.add(author)
    db.session.add(book)
    db.session.commit()

    author_schema = AuthorSchema()
    book_schema = BookSchema()

    dump_data_author = author_schema.dump(author)
    print(dump_data_author)

    dump_data_book = book_schema.dump(book)
    print(dump_data_book)

    json = [
        {'author_id': 1, 'title': 'Fight Club', 'id': 1}
    ]
    schema = BookSchema(many=True)
    print(schema.load(json))

    json = [
        {'books': [{'author_id': 1, 'title': 'Fight Club', 'id': 1}], 'name': 'Chuck Paluhniuk', 'id': 1}
    ]
    schema = AuthorSchema(many=True)
    print(schema.load(json))

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