# `yield` ile Dependency'ler { #dependencies-with-yield }

FastAPI, işini bitirdikten sonra <dfn title='bazen "exit code", "cleanup code", "teardown code", "closing code", "context manager exit code" vb. olarak da adlandırılır'>ek adımlar</dfn> çalıştıran dependency'leri destekler.

Bunu yapmak için `return` yerine `yield` kullanın ve ek adımları (kodu) `yield` satırından sonra yazın.

/// tip | İpucu

    Note over dep_req: Run code after yield
    Note over dep_req: ✅ Dependency closed
```

## 包含 `yield`、`HTTPException`、`except` 和后台任务的依赖项 { #dependencies-with-yield-httpexception-except-and-background-tasks }

带有 `yield` 的依赖项随着时间演进以涵盖不同的用例并修复了一些问题。

        assertEquals(3, fields.length);
        assertEquals("expires", fields[0]);
        assertEquals("start_time", fields[1]);
        assertEquals("end_time", fields[2]);
    }

    @Test
    public void test_indexAdminIntegerFields() {
        String[] fields = fessConfig.getIndexAdminIntegerFields().split(",");
        assertEquals(1, fields.length);

<div class="screenshot">
<img src="/img/tutorial/request-form-models/image01.png">
</div>

## Forbid Extra Form Fields { #forbid-extra-form-fields }

In some special use cases (probably not very common), you might want to **restrict** the form fields to only those declared in the Pydantic model. And **forbid** any **extra** fields.

/// note

This is supported since FastAPI version `0.114.0`. 🤓

///

from fastapi import Body, FastAPI
from pydantic import Field

app = FastAPI()


@app.post("/items/")
async def create_items(items: Annotated[list[int], Field(min_length=1), Body()]):
    return items
```

instead of:

```python
# DO NOT DO THIS
from typing import Annotated

from fastapi import FastAPI
from pydantic import Field, RootModel

app = FastAPI()

 * is stored in private fields; tests make use of the same package to
 * access those members directly.
 */
@ExtendWith(MockitoExtension.class)
class SmbComLockingAndXTest {

    /**
     * Helper for setting a field via reflection.
     */
    private static void setField(Object target, String name, Object value) {
        try {
            Field f = target.getClass().getDeclaredField(name);

    yield Item(name="Portal Gun", price=999.99)
```

For full control over SSE fields (`event`, `id`, `retry`, `comment`), yield `ServerSentEvent` instances:

```python
from collections.abc import AsyncIterable

from fastapi import FastAPI
from fastapi.sse import EventSourceResponse, ServerSentEvent

app = FastAPI()


@app.get("/events", response_class=EventSourceResponse)

    public void addField(final String key, final Object value) {
        fields.put(key, value);
    }

    public String getLogMessage() {
        return getUrl();
    }

    @Override
    public Map<String, Object> toSource() {
        final Map<String, Object> sourceMap = super.toSource();
        if (fields != null) {
            sourceMap.putAll(fields);
        }
        return sourceMap;
    }

    @Override

        return getUpdatedAt();
    }

    public void addField(final String key, final Object value) {
        fields.put(key, value);
    }

    @Override
    public Map<String, Object> toSource() {
        final Map<String, Object> sourceMap = super.toSource();
        if (fields != null) {
            sourceMap.putAll(fields);
        }
        return sourceMap;
    }

    @Override

        // Verify all fields through reflection
        Field field = response.getClass().getSuperclass().getSuperclass().getDeclaredField("totalParameterCount");
        field.setAccessible(true);
        assertEquals(totalParams, field.get(response));

        field = response.getClass().getSuperclass().getSuperclass().getDeclaredField("totalDataCount");
        field.setAccessible(true);