使用棉花糖而不重复自己 [英] Using Marshmallow without repeating myself

问题描述

根据Marshmallow官方文档，建议声明一个Schema，然后使用一个单独的类来接收已加载的数据，如下所示：

According to the official Marshmallow docs, it's recommended to declare a Schema and then have a separate class that receives loaded data, like this:

class UserSchema(Schema):
    name = fields.Str()
    email = fields.Email()
    created_at = fields.DateTime()

    @post_load
    def make_user(self, data):
        return User(**data)

但是，我的 User 类看起来像这样：

However, my User class would look something like this:

class User:
    def __init__(name, email, created_at):
        self.name = name
        self.email = email
        self.created_at = created_at

这似乎在不必要地重复自己，我真的不喜欢写该属性又命名了三遍。但是，我喜欢对定义良好的结构进行IDE自动补全和静态类型检查。

This seems like repeating myself unnecessarily and I really don't like having to write the attribute names three more times. However, I do like IDE autocompletion and static type checking on well-defined structures.

那么，是否有最佳实践根据棉花糖模式加载序列化数据而不定义另一个类？

So, is there any best practice for loading serialized data according to a Marshmallow Schema without defining another class?

推荐答案

对于普通的Python类，没有一种现成的方式为模式定义类而不重复字段名称。

For vanilla Python classes, there isn't an out-of-box way to define the class for the schema without repeating the field names.

例如，如果您使用的是SQLAlchemy，则可以直接使用 marshmallow_sqlalchemy.ModelSchema ：

If you're using SQLAlchemy for example, you can define the schema directly from the model with marshmallow_sqlalchemy.ModelSchema:

from marshmallow_sqlalchemy import ModelSchema
from my_alchemy_models import User

class UserSchema(ModelSchema):
    class Meta:
        model = User

同样适用于使用 flask_marshmallow.sqla.ModelSchema 。

Same applies to flask-sqlalchemy which uses flask_marshmallow.sqla.ModelSchema.

对于普通的Python类，您可以一次定义字段并将其用于模式和模型/类：

In the case of vanilla Python classes, you may define the fields once and use it for both schema and model/class:

USER_FIELDS = ('name', 'email', 'created_at')

class User:
    def __init__(self, name, email, created_at):
        for field in USER_FIELDS:
            setattr(self, field, locals()[field])

class UserSchema(Schema):
    class Meta:
        fields = USER_FIELDS

    @post_load
    def make_user(self, data):
        return User(**data)

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