首先，當然你可以自由混用 `Path`、`Query` 與請求 Body 參數的宣告，**FastAPI** 會知道該怎麼做。

你也可以將 Body 參數宣告為可選，方法是將預設值設為 `None`：

{* ../../docs_src/body_multiple_params/tutorial001_an_py310.py hl[18:20] *}

/// note | 注意

請注意，在此情況下，從 body 取得的 `item` 是可選的，因為它的預設值是 `None`。

///

## 多個 Body 參數 { #multiple-body-parameters }

在前一個範例中，路徑操作（path operation）會期望一個包含 `Item` 屬性的 JSON 主體，例如：

```JSON
{

        // Verify instance def is SESSION
        assertEquals(InstanceDefFactory.SESSION, pagerCreator.getInstanceDef());

        // Verify auto binding def is NONE
        assertEquals(AutoBindingDefFactory.NONE, pagerCreator.getAutoBindingDef());
    }

    // Test getPagerCustomizer when no customizer is set
    @Test
    public void test_getPagerCustomizer_null() {

    /**
     * Returns the range of this constraint, or {@code null} if none.
     * <p>
     * Note: only one, this method or {@link #getRecommendedVersion()} method must return non-{@code null} value.
     */
    @Nullable
    VersionRange getVersionRange();

    /**
     * Returns the recommended version of this constraint, or {@code null} if none.
     * <p>

     */
    boolean contains(@Nonnull Version version);

    /**
     * Returns the upper boundary of this range, or {@code null} if none.
     */
    @Nullable
    Boundary getUpperBoundary();

    /**
     * Returns the lower boundary of this range, or {@code null} if none.
     */
    @Nullable
    Boundary getLowerBoundary();

    /**
     * {@return the string representation of this version}
     */

 */
@Deprecated(since = "4.0.0")
public interface ToolchainsBuildingRequest {

    /**
     * Gets the global toolchains source.
     *
     * @return The global toolchains source or {@code null} if none.
     */
    Source getGlobalToolchainsSource();

    /**
     * Sets the global toolchains source. If both user toolchains and a global toolchains are given, the user toolchains
     * take precedence.
     *

     * Gets the installation settings source.
     *
     * @return the installation settings source or {@code null} if none
     */
    @Nonnull
    Optional<Source> getInstallationSettingsSource();

    /**
     * Gets the project settings source.
     *
     * @return the project settings source or {@code null} if none
     */
    @Nonnull
    Optional<Source> getProjectSettingsSource();

    /**

Аналогично, вы можете объявлять необязательные query-параметры, установив их значение по умолчанию, равное `None`:

{* ../../docs_src/query_params/tutorial002_py310.py hl[7] *}

В этом случае, параметр  `q` будет не обязательным и будет иметь значение `None` по умолчанию.

/// check | Важно

```

這表示 `item` 可以是 `int` 或 `str`。

#### 可能為 `None` { #possibly-none }

你可以宣告某個值可以是某個型別（例如 `str`），但它也可能是 `None`。

//// tab | Python 3.10+

```Python hl_lines="1"
{!> ../../docs_src/python_types/tutorial009_py310.py!}
```

////

使用 `str | None` 而不是單純的 `str`，可以讓編輯器幫你偵測錯誤，例如你以為某個值一定是 `str`，但它其實也可能是 `None`。

### 類別作為型別 { #classes-as-types }

你也可以用類別來宣告變數的型別。

app = FastAPI()


class Item(BaseModel):
    name: str
    price: float
    is_offer: bool | None = None


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


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


@app.put("/items/{item_id}")
def update_item(item_id: int, item: Item):

`id`’nin SQL veritabanındaki **primary key** olduğunu söyler (SQL primary key’leri hakkında daha fazlasını SQLModel dokümantasyonunda öğrenebilirsiniz).

    **Not:** primary key alanı için `int | None` kullanıyoruz; böylece Python kodunda *`id` olmadan bir nesne oluşturabiliriz* (`id=None`) ve veritabanının *kaydederken bunu üreteceğini* varsayarız. SQLModel, veritabanının `id` sağlayacağını anlar ve *veritabanı şemasında sütunu null olamayan bir `INTEGER`* olarak tanımlar. Detaylar için [primary...