/// tip | Consejo

Pydantic también tiene <a href="https://docs.pydantic.dev/latest/concepts/validators/#field-before-validator" class="external-link" target="_blank">`BeforeValidator`</a> y otros. 🤓

///

///

## Pasos Previos Antes de Iniciar { #previous-steps-before-starting }

Hay muchos casos en los que quieres realizar algunos pasos **antes de iniciar** tu aplicación.

Por ejemplo, podrías querer ejecutar **migraciones de base de datos**.

        } else {
          // Cannot use empty generator. Proceed with other generators.
        }
      } else {
        // never generated empty instance for this type before.
        Object emptyInstance = invokeGeneratorMethod(emptyGenerate);
        emptyInstanceGenerated.put(type.getType(), freshness.get());
        return emptyInstance;
      }
    }

        val result = nextUrl!!
        nextUrl = null
        canRemove = true
        return result
      }

      override fun remove() {
        check(canRemove) { "remove() before next()" }
        delegate.remove()
      }
    }
  }

  @Synchronized fun writeAbortCount(): Int = writeAbortCount

  @Synchronized fun writeSuccessCount(): Int = writeSuccessCount

///

## Schritte vor dem Start { #previous-steps-before-starting }

Es gibt viele Fälle, in denen Sie, **bevor Sie Ihre Anwendung starten**, einige Schritte ausführen möchten.

Beispielsweise möchten Sie möglicherweise **Datenbankmigrationen** ausführen.

        } else {
          // Cannot use empty generator. Proceed with other generators.
        }
      } else {
        // never generated empty instance for this type before.
        Object emptyInstance = invokeGeneratorMethod(emptyGenerate);
        emptyInstanceGenerated.put(type.getType(), freshness.get());
        return emptyInstance;
      }
    }

Falarei mais sobre imagens de contêiner, Docker, Kubernetes, etc. em um capítulo futuro: [FastAPI em contêineres - Docker](docker.md){.internal-link target=_blank}.

///

## Etapas anteriores antes de começar { #previous-steps-before-starting }

Há muitos casos em que você deseja executar algumas etapas **antes de iniciar** sua aplicação.

Por exemplo, você pode querer executar **migrações de banco de dados**.

    checkSerialization(Predicates.equalTo(null));
  }

  /**
   * Tests for Predicates.instanceOf(x). TODO: Fix the comment style after fixing annotation
   * stripper to remove comments properly. Currently, all tests before the comments are removed as
   * well.
   */
  @GwtIncompatible // Predicates.instanceOf
  public void testIsInstanceOf_apply() {
    Predicate<@Nullable Object> isInteger = Predicates.instanceOf(Integer.class);

	{"[):[o-FP", ""},     // Issue 12469 - there was no infinite loop for ARM; these are just sanity checks.
	{"[):[R0-FP", ""},
	{"(", ""}, // Issue 12466 - backed up before beginning of line.
}

var ppc64OperandTests = []operandTest{
	{"$((1<<63)-1)", "$9223372036854775807"},
	{"$(-64*1024)", "$-65536"},
	{"$(1024 * 8)", "$8192"},
	{"$-1", "$-1"},
	{"$-24(R4)", "$-24(R4)"},

		v.response(m.Seq, Response{
			Msg: m.Payload,
			Err: nil,
		})
	}
	// Close when EOF.
	if m.Flags&FlagEOF != 0 {
		// We must obtain the lock before closing
		// Otherwise others may pick up the error before close is called.
		v.respMu.Lock()
		v.closeLocked()
		v.respMu.Unlock()
		if debugReqs {
			fmt.Println(m.MuxID, c.String(), "handleMuxServerMsg: DELETING MUX")
		}