**Spoiler alert**: il tutorial - Guida Utente include:

* Dichiarazione di **parameters** da altri posti diversi come: **headers**, **cookies**, **form fields** e **files**.
* Come stabilire **vincoli di validazione** come `maximum_length` o `regex`.

func TestFields(t *testing.T) {
	for _, tt := range fieldstests {
		b := []byte(tt.s)
		a := Fields(b)

		// Appending to the results should not change future results.
		var x []byte
		for _, v := range a {
			x = append(v, 'z')
		}

		result := sliceOfString(a)
		if !slices.Equal(result, tt.a) {
			t.Errorf("Fields(%q) = %v; want %v", tt.s, a, tt.a)
			continue
		}

Pydantic heeft een speciaal gedrag wanneer je `Optional` of `Union[EenType, None]` gebruikt zonder een standaardwaarde, je kunt er meer over lezen in de Pydantic-documentatie over <a href="https://docs.pydantic.dev/2.3/usage/models/#required-fields" class="external-link" target="_blank">Verplichte optionele velden</a>.

///

## Type Hints met Metadata Annotaties

	}

	if createdByRel, ok := userSchema.Relationships.Relations["CreatedBy"]; ok {
		if createdByRel.FieldSchema != userSchema {
			t.Fatalf("expects same field schema, but got new %p, old %p", createdByRel.FieldSchema, userSchema)
		}
	} else {
		t.Fatalf("expects created by relations, but not found")
	}
}

func TestEmbeddedHas(t *testing.T) {
	type Toy struct {

   * AtomicInteger).
   */

  /** The number of occurrences of each element. */
  private final transient ConcurrentMap<E, AtomicInteger> countMap;

  // This constant allows the deserialization code to set a final field. This holder class
  // makes sure it is not initialized unless an instance is deserialized.
  private static class FieldSettersHolder {
    static final FieldSetter<? super ConcurrentHashMultiset<?>> COUNT_MAP_FIELD_SETTER =

   * calls to Builder.put (though we don't really care *which* two values if there were more than
   * two). These considerations lead us to have a field of type DuplicateKey in the Builder, which
   * will remember the first duplicate key we encountered. All later calls to buildOrThrow() can
   * mention that key with its values. Further duplicates might be added in the meantime but since

                    Severity.ERROR,
                    Version.BASE,
                    prefix + "systemPath",
                    d.getManagementKey(),
                    "must be omitted. This field may only be specified for a dependency with system scope.",
                    d);
        }

        if (request.getValidationLevel() >= ModelBuildingRequest.VALIDATION_LEVEL_MAVEN_2_0) {

///

### Использование Pydantic's `Required` вместо Ellipsis (`...`)

    val point = Point(null, 9L)
    assertThat(Point.ADAPTER.fromDer(bytes)).isEqualTo(point)
    assertThat(Point.ADAPTER.toDer(point)).isEqualTo(bytes)
  }

  @Test fun `point with both fields set`() {
    val bytes = "3006800109810109".decodeHex()
    val point = Point(9L, 9L)
    assertThat(Point.ADAPTER.fromDer(bytes)).isEqualTo(point)
    assertThat(Point.ADAPTER.toDer(point)).isEqualTo(bytes)
  }

Você pode utilizar todas as ferramentas e funcionalidades de validação que são utilizadas nos modelos do Pydantic, como tipos de dados diferentes e validações adicionei com `Field()`.

//// tab | Pydantic v2

```Python hl_lines="2  5-8  11"
{!> ../../docs_src/settings/tutorial001.py!}
```

////

//// tab | Pydantic v1

/// info