# Header Parameter Models { #header-parameter-models }

If you have a group of related **header parameters**, you can create a **Pydantic model** to declare them.

This would allow you to **re-use the model** in **multiple places** and also to declare validations and metadata for all the parameters at once. 😎

/// note

This is supported since FastAPI version `0.115.0`. 🤓

///

Declara los **parámetros de header** que necesitas en un **modelo Pydantic**, y luego declara el parámetro como `Header`:

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

**FastAPI** **extraerá** los datos para **cada campo** de los **headers** en el request y te dará el modelo Pydantic que definiste.

## Revisa la Documentación

Puedes ver los headers requeridos en la interfaz de documentación en `/docs`:

<div class="screenshot">

			for i, hdr := range hdrs {
				if i >= len(v.headers) {
					t.Fatalf("entry %d: unexpected header:\ngot %+v", i, *hdr)
				}
				if !reflect.DeepEqual(*hdr, *v.headers[i]) {
					t.Fatalf("entry %d: incorrect header:\ngot  %+v\nwant %+v", i, *hdr, *v.headers[i])
				}
			}
			if len(hdrs) != len(v.headers) {
				t.Fatalf("got %d headers, want %d headers", len(hdrs), len(v.headers))
			}

			for i, sum := range chksums {

import (
	"errors"
	"io"
	"unicode/utf8"
)

// A Reader implements the [io.Reader], [io.ReaderAt], [io.WriterTo], [io.Seeker],
// [io.ByteScanner], and [io.RuneScanner] interfaces by reading from
// a byte slice.
// Unlike a [Buffer], a Reader is read-only and supports seeking.
// The zero value for Reader operates like a Reader of an empty slice.
type Reader struct {
	s        []byte
	i        int64 // current reading index

func setEventStreamHeaders(w http.ResponseWriter) {
	w.Header().Set(xhttp.ContentType, "text/event-stream")
	w.Header().Set(xhttp.CacheControl, "no-cache") // nginx to turn off buffering
	w.Header().Set("X-Accel-Buffering", "no")      // nginx to turn off buffering
}

// Write http common headers
func setCommonHeaders(w http.ResponseWriter) {
	// Set the "Server" http header.
	w.Header().Set(xhttp.ServerInfo, MinioStoreName)

ativeSelectorCache","sortOrder","booleans","identifier","attributes","pseudos","rwhitespace","rcomma","rleadingCombinator","rdescend","rpseudo","ridentifier","matchExpr","ID","CLASS","TAG","ATTR","PSEUDO","CHILD","bool","needsContext","rinputs","rheader","rquickExpr","rsibling","runescape","funescape","escape","nonHex","high","String","fromCharCode","unloadHandler","setDocument","inDisabledFieldset","addCombinator","disabled","dir","next","childNodes","e","els","find","seed","m","nid","match","g...

# Header-параметры

Вы можете определить параметры заголовка таким же образом, как вы определяете параметры `Query`, `Path` и `Cookie`.

## Импорт `Header`

Сперва импортируйте `Header`:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Объявление параметров `Header`

Затем объявите параметры заголовка, используя ту же структуру, что и с `Path`, `Query` и `Cookie`.

 * limitations under the License.
 */
package okhttp3.internal.http2

import okio.ByteString
import okio.ByteString.Companion.encodeUtf8

/** HTTP header: the name is an ASCII string, but the value can be UTF-8. */
data class Header(
  /** Name in case-insensitive ASCII encoding. */
  @JvmField val name: ByteString,
  /** Value in UTF-8 encoding. */
  @JvmField val value: ByteString,
) {

{* ../../docs_src/header_param_models/tutorial001_an_py310.py hl[9:14,18] *}

O **FastAPI** irá **extrair** os dados de **cada campo** a partir dos **cabeçalhos** da requisição e te retornará o modelo do Pydantic que você definiu.

### Checando a documentação

Você pode ver os headers necessários na interface gráfica da documentação em `/docs`:

<%@page pageEncoding="UTF-8" contentType="text/html; charset=UTF-8"%>
<nav class="main-header navbar navbar-expand navbar-dark navbar-secondary">
	<ul class="navbar-nav">
		<li class="nav-item">
			<a class="nav-link" data-widget="pushmenu" href="#">
				<em class="fas fa-bars">
				<span class="sr-only"><la:message
						key="labels.admin_toggle_navi" /></span>
			</a>
		</li>
	</ul>
	<ul class="navbar-nav ml-auto">
		<c:if test="${eoled}">