# ボディ - フィールド { #body-fields }

`Query`や`Path`、`Body`を使って *path operation関数* のパラメータに追加のバリデーションやメタデータを宣言するのと同じように、Pydanticの`Field`を使ってPydanticモデルの内部でバリデーションやメタデータを宣言することができます。

## `Field`のインポート { #import-field }

まず、以下のようにインポートします:

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


/// warning | 注意

`Field`は他の全てのもの（`Query`、`Path`、`Body`など）とは違い、`fastapi`からではなく、`pydantic`から直接インポートされていることに注意してください。

///

	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		case "Bins":
			var zb0002 uint32

        // Assert that the public 'sids' field is initialized as expected
        assertEquals(sids, request.sids, "The 'sids' field should be initialized by the constructor.");

        // Use reflection to access and verify protected fields from the parent class DcerpcMessage
        Field ptypeField = DcerpcMessage.class.getDeclaredField("ptype");
        ptypeField.setAccessible(true);

     * This is a required field indicating success, failure, or running status.
     */
    @Required
    public String jobStatus;

    /**
     * The target or scope of the job execution.
     * This is a required field describing what the job operated on.
     */
    @Required
    public String target;

    /**
     * The type of script that was executed for this job.

	user, err := schema.Parse(&User{}, &sync.Map{}, schema.NamingStrategy{})
	if err != nil {
		t.Fatalf("failed to parse user with map, got error %v", err)
	}

	if field := user.FieldsByName["Attrs"]; field.DataType != "Map(String,String)" {
		t.Errorf("failed to parse user field Attrs")
	}
}

func TestParseSchemaWithPointerFields(t *testing.T) {
	user, err := schema.Parse(&User{}, &sync.Map{}, schema.NamingStrategy{})
	if err != nil {

        return supportedFields;
    }

    /**
     * Returns the tag field names.
     * @return The tag field names.
     */
    public String[] getTagFieldNames() {
        return tagFieldNames;
    }

    /**
     * Returns the role field name.
     * @return The role field name.
     */
    public String getRoleFieldName() {
        return roleFieldName;
    }

    /**

func (z *nsScannerOptions) DecodeMsg(dc *msgp.Reader) (err error) {
	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		case "id":
			z.DiskID, err = dc.ReadString()

from fastapi import FastAPI
from pydantic import BaseModel, Field

app = FastAPI()


class Item(BaseModel):
    name: str = Field(examples=["Foo"])
    description: str | None = Field(default=None, examples=["A very nice Item"])
    price: float = Field(examples=[35.4])
    tax: float | None = Field(default=None, examples=[3.2])


@app.put("/items/{item_id}")
async def update_item(item_id: int, item: Item):

from typing import Annotated

import pytest
from dirty_equals import IsOneOf
from fastapi import FastAPI, Query
from fastapi.testclient import TestClient
from inline_snapshot import snapshot
from pydantic import BaseModel, Field

app = FastAPI()

# =====================================================================================
# Without aliases


@app.get("/required-str")
async def read_required_str(p: str):

func (z *BatchJobExpire) DecodeMsg(dc *msgp.Reader) (err error) {
	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		case "APIVersion":
			z.APIVersion, err = dc.ReadString()