为模型定义模式
声明映射到模型的字段
为模型定义模式 是 CoddyKit 上的免费 Flask Academy 课时。 这是第 2 节课，共 4 节。 你可以在下方免费阅读本课时的完整内容 — 然后在浏览器中使用内置代码编辑器和全天候 AI 导师进行实践。 这是 Flask Academy 学习路径的一部分，你的进度在网页和 CoddyKit 应用中同步。 Flask Academy 课程共包含 4 节课。
本课时的部分内容尚未翻译，以英文显示。
What a Schema Is
A Schema is a Python class that lists the fields your data should have. It mirrors a model but lives separately, just for input and output.
Subclass Schema
Every schema inherits from Marshmallow's base Schema class. Naming it after your model, like UserSchema, keeps the intent obvious at a glance.
class UserSchema(Schema):
passDeclare Fields
Inside the class you add attributes from the fields module. Each one names a key that will appear in your serialized JSON output.
id = fields.Int()
name = fields.Str()Field Types Matter
Pick a field type that matches the data: Int, Str, Bool, Float, or DateTime. The type controls how values are formatted and validated.
active = fields.Bool()
score = fields.Float()Dates Done Right
A DateTime field serializes Python datetimes into clean ISO strings automatically. No more manual formatting scattered across your views.
created_at = fields.DateTime()Mark Required Fields
Pass required=True to a field so loading fails if it is missing. This is your first taste of validation baked right into the schema.
email = fields.Str(required=True)Leave Secrets Out
Only list fields you want to expose. By simply not declaring password_hash, the schema can never leak it into a response.
Rename with data_key
Want camelCase JSON from a snake_case attribute? Use data_key to map an internal name to a different external key.
first_name = fields.Str(data_key="firstName")dump_only Fields
Some fields, like an id, should appear in output but never be accepted as input. Mark them dump_only to keep them read-only.
id = fields.Int(dump_only=True)Instantiate the Schema
You create one instance to reuse: user_schema equals UserSchema(). Pass many=True later when you serialize a whole list.
user_schema = UserSchema()One Schema, Two Jobs
This single class will both dump models to JSON and load JSON back into checked data. You define the shape once and use it both directions.
Quick Check
You want id readable in output but never accepted as input.
Recap
A Schema subclass declares typed fields that map to your model. Options like required, dump_only, and data_key shape exactly what goes in and out.
常见问题解答
「为模型定义模式」课时是免费的吗？
是的 — 「为模型定义模式」的完整文本可在网页上免费阅读。要进行交互式练习（内置代码编辑器和全天候 AI 导师）并解锁 Flask Academy 课程的其余内容，请升级到 CoddyKit PRO。 Flask Academy 课程共包含 4 节课。
「为模型定义模式」这节课中我会学到什么？
声明映射到模型的字段 你通过在浏览器中直接运行的动手代码来练习 Flask Academy，全天候 AI 导师会在你学习这节课的过程中回答你的问题。
学习 Flask Academy 需要有经验吗？
无需任何先前经验。CoddyKit 上的 Flask Academy 课程适合初学者到高级学习者，你可以从这里开始或从头开始，按照自己的节奏学习。 这是第 2 节课，共 4 节。
「为模型定义模式」课时需要多长时间？
大多数 CoddyKit 课程大约需要 5–10 分钟。每节课都很精短且互动，所以你能稳步进步，并在网页和应用中从离开的地方继续。
我能在这节 Flask Academy 课中编写并运行代码吗？
能。每节 Flask Academy 课都包含内置代码编辑器，你可以在浏览器中直接编写并运行真实代码，并获得即时 AI 反馈 — 无需本地设置。