tax: Union[float, None] = None
    tags: set[str] = set()


@app.post(
    "/items/",
    response_model=Item,
    summary="Create an item",
    response_description="The created item",
)
async def create_item(item: Item):
    """
    Create an item with all the information:

    - **name**: each item must have a name
    - **description**: a long description
    - **price**: required

├── concurrent/                 # Async patterns (Deferred/Promise)
└── util/                      # Utilities
```

### Key Design Patterns

- **Builder**: SuggesterBuilder, SuggestRequestBuilder
- **Facade**: Suggester (main entry point)
- **Composite**: NormalizerChain, ReadingConverterChain
- **Strategy**: Normalizer, ReadingConverter, ContentsParser
- **Deferred/Promise**: Async operations

### Index Alias Strategy

///

/// tip | Порада

Якщо Вам потрібно викликати `async`-функції у ваших тестах, окрім відправлення запитів до FastAPI-застосунку (наприклад, асинхронні функції роботи з базою даних), перегляньте [Асинхронні тести](../advanced/async-tests.md){.internal-link target=_blank} у розширеному керівництві.

///

## Розділення тестів

            byte[] buffer = new byte[256];
            System.arraycopy(SMBUtil.SMB2_HEADER, 0, buffer, 0, 4);
            // Set up async message fields
            SMBUtil.writeInt4(ServerMessageBlock2.SMB2_FLAGS_ASYNC_COMMAND, buffer, 16); // flags with async
            SMBUtil.writeInt8(789L, buffer, 32); // async ID
            SMBUtil.writeInt8(456L, buffer, 40); // session ID
            return buffer;
        }

<details markdown="1">
<summary>Or use <code>async def</code>...</summary>

If your code uses `async` / `await`, use `async def`:

```Python hl_lines="9  14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


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


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

@dataclass
class Author:
    name: str
    items: list[Item] = field(default_factory=list)  # (3)


app = FastAPI()


@app.post("/authors/{author_id}/items/", response_model=Author)  # (4)
async def create_author_items(author_id: str, items: list[Item]):  # (5)
    return {"name": author_id, "items": items}  # (6)


@app.get("/authors/", response_model=list[Author])  # (7)
def get_authors():  # (8)

@dataclass
class Author:
    name: str
    items: list[Item] = field(default_factory=list)  # (3)


app = FastAPI()


@app.post("/authors/{author_id}/items/", response_model=Author)  # (4)
async def create_author_items(author_id: str, items: list[Item]):  # (5)
    return {"name": author_id, "items": items}  # (6)


@app.get("/authors/", response_model=list[Author])  # (7)
def get_authors():  # (8)

<details markdown="1">
<summary>또는 <code>async def</code> 사용하기...</summary>

여러분의 코드가 `async` / `await`을 사용한다면, `async def`를 사용하십시오.

```Python hl_lines="9 14"
from typing import Union

from fastapi import FastAPI

app = FastAPI()


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


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

class JsonApiError(BaseModel):
    errors: list[Error]


@app.get(
    "/a/{id}",
    response_class=JsonApiResponse,
    responses={422: {"description": "Error", "model": JsonApiError}},
)
async def a(id):
    pass  # pragma: no cover


client = TestClient(app)


def test_openapi_schema():
    response = client.get("/openapi.json")
    assert response.status_code == 200, response.text

    price: float
    tags: list[str] = field(default_factory=list)
    description: Union[str, None] = None
    tax: Union[float, None] = None


app = FastAPI()


@app.get("/item", response_model=Item)
async def read_item():
    return {
        "id": uuid.uuid4(),
        "name": "Island In The Moon",
        "price": 12.99,
        "description": "A place to be be playin' and havin' fun",
        "tags": ["breater"],