if (value instanceof final LocalDateTime ldt) {
            final ZonedDateTime zdt = ZonedDateTime.of(ldt, ZoneId.systemDefault());
            super.addFieldToSource(sourceMap, field, DateTimeFormatter.ISO_INSTANT.format(zdt));
        } else {
            super.addFieldToSource(sourceMap, field, value);
        }
    }

    @Override

@app.get("/items/stream-invalid")
async def stream_items_invalid() -> AsyncIterable[Item]:
    yield {"name": "valid", "price": 1.0}
    yield {"name": "invalid", "price": "not-a-number"}


@app.get("/items/stream-invalid-sync")
def stream_items_invalid_sync() -> Iterable[Item]:
    yield {"name": "valid", "price": 1.0}
    yield {"name": "invalid", "price": "not-a-number"}


client = TestClient(app)

`Depends(scope="request")` (varsayılan) kullanıldığında ise `yield` sonrasındaki çıkış kodu, response gönderildikten sonra çalıştırılır.

Daha fazlasını [`yield` ile Dependency'ler - Erken çıkış ve `scope`](../tutorial/dependencies/dependencies-with-yield.md#early-exit-and-scope) dokümantasyonunda okuyabilirsiniz.

### `yield` ve `StreamingResponse` ile dependency'ler, Teknik Detaylar { #dependencies-with-yield-and-streamingresponse-technical-details }

///

### `yield from` { #yield-from }

When you are iterating over something, like a file-like object, and then you are doing `yield` for each item, you could also use `yield from` to yield each item directly and skip the `for` loop.

This is not particular to FastAPI, it's just Python, but it's a nice trick to know. 😎

        String[] fields = (String[]) propMap.get(LOGGING_SEARCH_DOCS_FIELDS);
        if (fields == null) {
            fields = split(getLoggingSearchDocsFields(), ",").get(stream -> stream.map(String::trim).toArray(n -> new String[n]));
            propMap.put(LOGGING_SEARCH_DOCS_FIELDS, fields);
        }
        return fields;
    }

    String getSchedulerTargetName();

使用 `Depends(scope="function")` 時，`yield` 之後的結束程式碼會在「路徑操作函式」執行完畢後立刻執行，在回應發送回客戶端之前。

而當使用 `Depends(scope="request")`（預設值）時，`yield` 之後的結束程式碼會在回應送出之後才執行。

你可以在文件中閱讀更多：[含有 `yield` 的相依 - 提前結束與 `scope`](../tutorial/dependencies/dependencies-with-yield.md#early-exit-and-scope)。

### 含有 `yield` 與 `StreamingResponse` 的相依，技術細節 { #dependencies-with-yield-and-streamingresponse-technical-details }

在 FastAPI 0.118.0 之前，如果你使用含有 `yield` 的相依，它會在「路徑操作函式」回傳之後、發送回應之前，執行結束程式碼。

    async def lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    @asynccontextmanager
    async def router_lifespan(app: FastAPI) -> AsyncGenerator[dict[str, bool], None]:
        yield {"router": True}

    @asynccontextmanager
    async def sub_router_lifespan(app: FastAPI) -> AsyncGenerator[None, None]:
        yield

    sub_router = APIRouter(lifespan=sub_router_lifespan)

///

### `yield from` { #yield-from }

Wenn Sie über etwas iterieren, z. B. ein dateiähnliches Objekt, und dann für jedes Element `yield` verwenden, könnten Sie auch `yield from` verwenden, um jedes Element direkt weiterzugeben und die `for`-Schleife zu sparen.

            final ASN1EncodableVector fields = new ASN1EncodableVector();
            final int res = getResult();
            if (res != UNSPECIFIED_RESULT) {
                fields.add(new DERTaggedObject(true, 0, new ASN1Enumerated(res)));
            }
            final ASN1ObjectIdentifier mech = getMechanism();
            if (mech != null) {
                fields.add(new DERTaggedObject(true, 1, mech));
            }

///

### `yield from` { #yield-from }

Cuando estés iterando sobre algo, como un objeto tipo archivo, y estés haciendo `yield` para cada elemento, también podrías usar `yield from` para hacer `yield` de cada elemento directamente y saltarte el `for`.