### Step 3: create a *path operation* { #step-3-create-a-path-operation }

#### Path { #path }

"Path" here refers to the last part of the URL starting from the first `/`.

So, in a URL like:

```
https://example.com/items/foo
```

...the path would be:

```
/items/foo
```

/// info

A "path" is also commonly called an "endpoint" or a "route".

///

## Declarar atributos del modelo

Después puedes utilizar `Field` con los atributos del modelo:

{* ../../docs_src/body_fields/tutorial001_an_py310.py hl[11:14] *}

`Field` funciona de la misma manera que `Query`, `Path` y `Body`, tiene todos los mismos parámetros, etc.

/// note | Detalles técnicos

        wagon.addExpectedContent("path", "lower-case-checksum");
        wagon.addExpectedContent("path.sha1", "2a25dc564a3b34f68237fc849066cbc7bb7a36a1");
        wagonManager.getArtifact(artifact, repo, null, false);

        wagon.clearExpectedContent();
        wagon.addExpectedContent("path", "upper-case-checksum");
        wagon.addExpectedContent("path.sha1", "B7BB97D7D0B9244398D9B47296907F73313663E6");

## Usa el objeto `Request` directamente

Imaginemos que quieres obtener la dirección IP/host del cliente dentro de tu *path operation function*.

Para eso necesitas acceder al request directamente.

{* ../../docs_src/using_request_directly/tutorial001.py hl[1,7:8] *}

Al declarar un parámetro de *path operation function* con el tipo siendo `Request`, **FastAPI** sabrá pasar el `Request` en ese parámetro.

/// tip | Consejo

        // Implementation uses dir.getPath() to check if file should be in that path
        SmbFilenameFilter filter = (dir, name) -> {
            if (dir == null)
                return false;
            String path = dir.getPath();
            // Accept files in /share/folder/ that are text files
            return path.equals("/share/folder/") && name != null && name.endsWith(".txt");
        };

ItemsService.createItemItemsPost({name: "Plumbus", price: 5})
```

...that's because the client generator uses the OpenAPI internal **operation ID** for each *path operation*.

OpenAPI requires that each operation ID is unique across all the *path operations*, so FastAPI uses the **function name**, the **path**, and the **HTTP method/operation** to generate that operation ID, because that way it can make sure that the operation IDs are unique.

    }

    // Happy path: handleDFSReferral returns a resolved path
    @Test
    @DisplayName("handleDFSReferral returns resolved UNC path as stubbed")
    void handleDfsReferralValidInputs() {
        // Edge-like Windows UNC-style: a single backslash in the path
        String reqPath = "\\";
        String resolved = "smb://server/share/path";

Primero crea un nuevo `APIRouter` que contendrá uno o más callbacks.

{* ../../docs_src/openapi_callbacks/tutorial001.py hl[3,25] *}

### Crear la *path operation* del callback

Para crear la *path operation* del callback utiliza el mismo `APIRouter` que creaste anteriormente.

Debería verse como una *path operation* normal de FastAPI:

* Probablemente debería tener una declaración del body que debería recibir, por ejemplo `body: InvoiceEvent`.

        final String path = ClassUtil.getPackageName(this.getClass()).replaceAll("\\.", "/") + "/aaa.html";
        final String contentType = MimeTypeUtil.guessContentType(path);
        assertEquals("text/html", contentType);
    }

    /**
     * @throws Exception
     */
    @Test
    public void testGetFromStream_gif() throws Exception {

	// Points to relative path to certs directory and is <value-of-certs-dir>/CAs
	globalCertsCADir = defaultCertsCADir
)

// Get - returns current directory.
func (dir *ConfigDir) Get() string {
	return dir.path
}

// Attempts to create all directories, ignores any permission denied errors.
func mkdirAllIgnorePerm(path string) error {
	err := os.MkdirAll(path, 0o700)
	if err != nil {