## La aplicación normal de **FastAPI** { #the-normal-fastapi-app }

Primero veamos cómo se vería la aplicación API normal antes de agregar el callback.

Tendrá una *path operation* que recibirá un cuerpo `Invoice`, y un parámetro de query `callback_url` que contendrá la URL para el callback.

Esta parte es bastante normal, probablemente ya estés familiarizado con la mayor parte del código:

  public void testNoExceptionsThrown() throws IOException {
    Closer closer = new Closer(suppressor);

    TestCloseable c1 = closer.register(TestCloseable.normal());
    TestCloseable c2 = closer.register(TestCloseable.normal());
    TestCloseable c3 = closer.register(TestCloseable.normal());

    assertFalse(c1.isClosed());
    assertFalse(c2.isClosed());
    assertFalse(c3.isClosed());

    closer.close();

{* ../../docs_src/dependencies/tutorial007_py310.py hl[5:6] *}

/// tip | Consejo

Puedes usar funciones `async` o regulares.

**FastAPI** hará lo correcto con cada una, igual que con dependencias normales.

///

## Una dependencia con `yield` y `try` { #a-dependency-with-yield-and-try }

Si usas un bloque `try` en una dependencia con `yield`, recibirás cualquier excepción que se haya lanzado al usar la dependencia.

### Raise exceptions { #raise-exceptions }

These dependencies can `raise` exceptions, the same as normal dependencies:

{* ../../docs_src/dependencies/tutorial006_an_py310.py hl[10,15] *}

### Return values { #return-values }

And they can return values or not, the values won't be used.

### Exceptions auslösen { #raise-exceptions }

Die Abhängigkeiten können Exceptions `raise`n, genau wie normale Abhängigkeiten:

{* ../../docs_src/dependencies/tutorial006_an_py310.py hl[10,15] *}

### Rückgabewerte { #return-values }

Und sie können Werte zurückgeben oder nicht, die Werte werden nicht verwendet.

    * Bu, external geliştiricinin sağladığı bir *external API*'ye (sizin API'nizden) bir POST request gönderilerek yapılır (işte bu "callback"tir).

## Normal **FastAPI** uygulaması { #the-normal-fastapi-app }

Önce callback eklemeden önce normal API uygulamasının nasıl görüneceğine bakalım.

Bir `Invoice` body alacak bir *path operation*'ı ve callback için URL'yi taşıyacak `callback_url` adlı bir query parametresi olacak.

            final long time = Joda.forPattern(format).parseMillis(value);
            return new Date(time);
        } catch (final Exception e) {
            return null;
        }
    }

    /**
     * Formats a Date object to ISO datetime string format in UTC timezone.
     *
     * @param date the date to format
     * @return formatted date string, or empty string if date is null
     */

    xsi:schemaLocation="http://maven.apache.org/ASSEMBLY/2.1.0 http://maven.apache.org/xsd/assembly-2.1.0.xsd">
  <id>bin</id>
  <formats>
    <format>zip</format>
    <format>tar.gz</format>
  </formats>
  <componentDescriptors>
    <componentDescriptor>src/assembly/component.xml</componentDescriptor>
  </componentDescriptors>

// Invariant: logicalRemaining >= physicalRemaining
type fileState interface {
	logicalRemaining() int64
	physicalRemaining() int64
}

// allowedFormats determines which formats can be used.
// The value returned is the logical OR of multiple possible formats.
// If the value is FormatUnknown, then the input Header cannot be encoded
// and an error is returned explaining why.
//

    font-weight: 400;
    font-style: normal
}

@font-face {
    font-family: cash-market;
    src: url("https://cash-f.squarecdn.com/static/fonts/cash-market/v2/CashMarket-Medium.woff2") format("woff2");
    font-weight: 500;
    font-style: normal
}

@font-face {
    font-family: cash-market;