# Body – Felder { #body-fields }

So wie Sie zusätzliche Validierung und Metadaten in Parametern der *Pfadoperation-Funktion* mittels `Query`, `Path` und `Body` deklarieren, können Sie auch innerhalb von Pydantic-Modellen zusätzliche Validierung und Metadaten deklarieren, mittels Pydantics `Field`.

## `Field` importieren { #import-field }

Importieren Sie es zuerst:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[4] *}

/// warning | Achtung

# FastAPI

<style>
.md-content .md-typeset h1 { display: none; }
</style>

<p align="center">
  <a href="https://fastapi.tiangolo.com"><img src="https://fastapi.tiangolo.com/img/logo-margin/logo-teal.png" alt="FastAPI"></a>
</p>
<p align="center">
    FastAPI 框架，高性能，易于学习，高效编码，生产可用
</p>
<p align="center">
<a href="https://github.com/fastapi/fastapi/actions?query=workflow%3ATest+event%3Apush+branch%3Amaster" target="_blank">

Eğer tarayıcınızda şu bağlantıyı:

```
http://127.0.0.1:8000/items/foo-item
```

...`needy` parametresini eklemeden açarsanız şuna benzer bir hata ile karşılaşırsınız:

```JSON
{
  "detail": [
    {
      "type": "missing",
      "loc": [
        "query",
        "needy"
      ],
      "msg": "Field required",

[<a href="#Go_1.18">Go 1.18</a>].
</p>

<pre>
type Reader interface {
	Read(p []byte) (n int, err error)
	Close() error
}

type Writer interface {
	Write(p []byte) (n int, err error)
	Close() error
}

// ReadWriter's methods are Read, Write, and Close.
type ReadWriter interface {
	Reader  // includes methods of Reader in ReadWriter's method set

/*
 * Copyright (C) 2015 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

///

### Pydantic v1 und v2 in derselben App { #pydantic-v1-and-v2-on-the-same-app }

Es wird von Pydantic **nicht unterstützt**, dass ein Pydantic‑v2‑Modell Felder hat, die als Pydantic‑v1‑Modelle definiert sind, und umgekehrt.

```mermaid
graph TB
    subgraph "❌ Nicht unterstützt"
        direction TB
        subgraph V2["Pydantic-v2-Modell"]

   * value returned by this method is the {@code i} in that range such that {@code allRequired[i]}
   * is as close as possible to the center of the range [{@code from}, {@code to}]. Choosing the
   * value closest to the center of the range first is the most efficient strategy because it
   * minimizes the size of the subranges from which the remaining selections must be done.
   */

/*
 * Copyright (C) 2016 Square, Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,

Use American English spelling, for example:

* `color` (not `colour`)
* `initialize` (not `initialise`)
* `behavior` (not `behaviour`)
* `analyze` (not `analyse`)
* `organization` (not `organisation`)
* `center` (not `centre`)
* `canceled` (not `cancelled`)
* `labeled` (not `labelled`)

### Rationale for American English

American English was chosen for the following reasons:

<p align="center"><img width="350px" src="jstream.png" alt="jstream"/></p>

#

[![GoDoc](https://godoc.org/github.com/bcicen/jstream?status.svg)](https://godoc.org/github.com/bcicen/jstream)


`jstream` is a streaming JSON parser and value extraction library for Go.