# Body - Fields

The same way you can declare additional validation and metadata in *path operation function* parameters with `Query`, `Path` and `Body`, you can declare validation and metadata inside of Pydantic models using Pydantic's `Field`.

## Import `Field`

First, you have to import it:

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


/// warning

  // APIs may return other objects types at their discretion, such as error conditions, requests for alternate representations, or other operation specific behavior.
  // This value will be null if an APIService reports subresources but supports no operations on the parent resource
  optional k8s.io.apimachinery.pkg.apis.meta.v1.GroupVersionKind responseKind = 2;

which in turn are made up of memory operations.
</p>

<p>
A <i>memory operation</i> is modeled by four details:
</p>
<ul>
	<li>its kind, indicating whether it is an ordinary data read, an ordinary data write,
    or a <i>synchronizing operation</i> such as an atomic data access,
	a mutex operation, or a channel operation,</li>
	<li>its location in the program,</li>

		return
	}

	// Validate operation
	operation := mux.Vars(r)["operation"]
	if operation != "attach" && operation != "detach" {
		writeErrorResponseJSON(ctx, w, errorCodes.ToAPIErr(ErrAdminInvalidArgument), r.URL)
		return
	}

	isAttach := operation == "attach"

	// Validate API arguments in body.
	password := cred.SecretKey

///

```Python hl_lines="22"
{!> ../../docs_src/dependencies/tutorial005.py!}
```

////

/// info

Notice that we are only declaring one dependency in the *path operation function*, the `query_or_cookie_extractor`.

But **FastAPI** will know that it has to solve `query_extractor` first, to pass the results of that to `query_or_cookie_extractor` while calling it.

///

```mermaid

  override fun checkClientTrusted(
    chain: Array<out X509Certificate>,
    authType: String?,
  ) = throw CertificateException("Unsupported operation")

  override fun checkServerTrusted(
    chain: Array<out X509Certificate>,
    authType: String,
  ) = throw CertificateException("Unsupported operation")

import com.google.common.annotations.GwtCompatible;

/**
 * An object that can perform a {@link #tearDown} operation.
 *
 * @author Kevin Bourrillion
 * @since 10.0
 */
@FunctionalInterface
@GwtCompatible
@ElementTypesAreNonnullByDefault
public interface TearDown {
  /**
   * Performs a <b>single</b> tear-down operation. See test-libraries-for-java's {@code
   * com.google.common.testing.junit3.TearDownTestCase} and {@code

## Use the `Request` object directly

Let's imagine you want to get the client's IP address/host inside of your *path operation function*.

For that you need to access the request directly.

```Python hl_lines="1  7-8"
{!../../docs_src/using_request_directly/tutorial001.py!}
```

By declaring a *path operation function* parameter with the type being the `Request` **FastAPI** will know to pass the `Request` in that parameter.

/// tip

"Шлях" (path) також зазвичай називають "ендпоінтом" (endpoint) або "маршрутом" (route).

///

При створенні API, "шлях" є основним способом розділення "завдань" і "ресурсів".
#### Operation

"Операція" (operation) тут означає один з "методів" HTTP.

Один з:

* `POST`
* `GET`
* `PUT`
* `DELETE`

...та більш екзотичних:

* `OPTIONS`
* `HEAD`
* `PATCH`
* `TRACE`

  public void testRemove_nullKeyQueriesUnsupported() {
    try {
      assertFalse(getMap().remove(null, v3()));
    } catch (NullPointerException tolerated) {
      // since the operation would be a no-op, the exception is not required
    }
    expectUnchanged();
  }

  @MapFeature.Require(value = SUPPORTS_REMOVE, absent = ALLOWS_NULL_VALUE_QUERIES)