POLICY_INFO_PRIMARY_DOMAIN = 3,
		POLICY_INFO_ACCOUNT_DOMAIN = 5,
		POLICY_INFO_SERVER_ROLE    = 6,
		POLICY_INFO_MODIFICATION   = 9,
		POLICY_INFO_DNS_DOMAIN     = 12
	};

	typedef [switch_type(short)] union {
		[case(POLICY_INFO_ACCOUNT_DOMAIN)] LsarDomainInfo account_domain;
		[case(POLICY_INFO_DNS_DOMAIN)] LsarDnsDomainInfo dns_domain;
	} LsarPolicyInfo;

	typedef struct {
		sid_t *sid;
	} LsarSidPtr;

/// note | Observação

O FastAPI saberá que o valor de `q` não é obrigatório por causa do valor padrão `= None`.

O `Union` em `Union[str, None]` não é utilizado pelo FastAPI, mas permite ao seu editor de texto lhe dar um suporte melhor e detectar erros.

///

## Sem o Pydantic

/// note

FastAPI will know that the value of `q` is not required because of the default value `= None`.

The `str | None` (Python 3.10+) or `Union` in `Union[str, None]` (Python 3.8+) is not used by FastAPI to determine that the value is not required, it will know it's not required because it has a default value of `= None`.

То же самое произошло бы, если бы у вас было что-то вроде <abbr title='Union разных типов буквально означает "любой из перечисленных типов".'>Union</abbr> различных типов и один или несколько из них не являлись бы допустимыми типами для Pydantic. Например, такой вариант приведет к ошибке 💥:

cases section below.

To access a struct, union, or enum type directly, prefix it with
struct_, union_, or enum_, as in C.struct_stat. The size of any C type
T is available as C.sizeof_T, as in C.sizeof_struct_stat. These
special prefixes means that there is no way to directly reference a C
identifier that starts with "struct_", "union_", "enum_", or
"sizeof_", such as a function named "struct_function".

q: str | None = None
```

////

//// tab | Python 3.8+

```Python
q: Union[str, None] = None
```

////

What we will do is wrap that with `Annotated`, so it becomes:

//// tab | Python 3.10+

```Python
q: Annotated[str | None] = None
```

////

//// tab | Python 3.8+

```Python
q: Annotated[Union[str, None]] = None
```

////

### ایجاد کنید
* فایلی به نام `main.py` با محتوای زیر ایجاد کنید:

```Python
from typing import Union

from fastapi import FastAPI

app = FastAPI()


@app.get("/")
def read_root():
    return {"Hello": "World"}


@app.get("/items/{item_id}")
def read_item(item_id: int, q: Union[str, None] = None):
    return {"item_id": item_id, "q": q}
```

<details markdown="1">

        }

        @Override
        public void decode_out(NdrBuffer _src) throws NdrException {
            this.level = _src.dec_ndr_long();
            _src.dec_ndr_long(); /* union discriminant */
            final int _infop = _src.dec_ndr_long();
            if (_infop != 0) {
                if (this.info == null) { /* YOYOYO */
                    this.info = new ShareInfoCtr0();

## 必須にする

これ以上、バリデーションやメタデータを宣言する必要のない場合は、デフォルト値を指定しないだけでクエリパラメータ`q`を必須にすることができます。以下のように:

```Python
q: str
```

以下の代わりに:

```Python
q: Union[str, None] = None
```

現在は以下の例のように`Query`で宣言しています:

```Python
q: Union[str, None] = Query(default=None, min_length=3)
```

そのため、`Query`を使用して必須の値を宣言する必要がある場合は、第一引数に`...`を使用することができます:

* 만약 매개변수가 **Pydantic 모델** 타입으로 선언되어 있으면, 요청 **본문**으로 해석될 것입니다.

/// note | 참고

FastAPI는 `q`의 값이 필요없음을 알게 될 것입니다. 기본 값이 `= None`이기 때문입니다.

`Union[str, None]`에 있는 `Union`은 FastAPI에 의해 사용된 것이 아니지만, 편집기로 하여금 더 나은 지원과 에러 탐지를 지원할 것입니다.

///

## Pydantic없이