### Dependencias con `yield` y `scope` { #dependencies-with-yield-and-scope }

En la versión 0.121.0, FastAPI agregó soporte para `Depends(scope="function")` para dependencias con `yield`.

Usando `Depends(scope="function")`, el código de salida después de `yield` se ejecuta justo después de que la *path operation function* termina, antes de que la response se envíe de vuelta al cliente.

# Background Tasks - `BackgroundTasks`

You can declare a parameter in a *path operation function* or dependency function with the type `BackgroundTasks`, and then you can use it to schedule the execution of background tasks after the response is sent.

You can import it directly from `fastapi`:

```python
from fastapi import BackgroundTasks
```

            ws.onmessage = function(event) {
                var messages = document.getElementById('messages')
                var message = document.createElement('li')
                var content = document.createTextNode(event.data)
                message.appendChild(content)
                messages.appendChild(message)
            };
            function sendMessage(event) {

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import java.util.ListIterator;
import org.jspecify.annotations.Nullable;

/**
 * An iterator that transforms a backing list iterator; for internal use. This avoids the object
 * overhead of constructing a {@link Function} for internal methods.
 *
 * @author Louis Wasserman
 */
@GwtCompatible

package com.google.common.collect;

import com.google.common.annotations.GwtCompatible;
import com.google.common.base.Function;
import java.util.ListIterator;
import org.jspecify.annotations.Nullable;

/**
 * An iterator that transforms a backing list iterator; for internal use. This avoids the object
 * overhead of constructing a {@link Function} for internal methods.
 *
 * @author Louis Wasserman
 */
@GwtCompatible

        </ul>
        <script>
        var ws = null;
            function connect(event) {
                var itemId = document.getElementById("itemId")
                var token = document.getElementById("token")
                ws = new WebSocket("ws://localhost:8000/items/" + itemId.value + "/ws?token=" + token.value);
                ws.onmessage = function(event) {
                    var messages = document.getElementById('messages')

        </ul>
        <script>
        var ws = null;
            function connect(event) {
                var itemId = document.getElementById("itemId")
                var token = document.getElementById("token")
                ws = new WebSocket("ws://localhost:8000/items/" + itemId.value + "/ws?token=" + token.value);
                ws.onmessage = function(event) {
                    var messages = document.getElementById('messages')

   */
  fun <T : Any> tag(
    type: KClass<T>,
    computeIfAbsent: () -> T,
  ): T

  /**
   * Returns the tag attached with [type] as a key. If it is absent, then [computeIfAbsent] is
   * called and that value is both inserted and returned.
   *
   * If multiple calls to this function are made concurrently with the same [type], multiple values

def dep():
    pass


def test_depends_hashable():
    dep()  # just for coverage
    d1 = Depends(dep)
    d2 = Depends(dep)
    d3 = Depends(dep, scope="function")
    d4 = Depends(dep, scope="function")

    s1 = Security(dep)
    s2 = Security(dep)

    assert hash(d1) == hash(d2)
    assert hash(s1) == hash(s2)
    assert hash(d1) != hash(d3)

// check for errors, but do not perform any combining of the results
// of child nodes. The final result row is returned after all rows are
// processed, and the `getAggregate` function is called.

func (e *AliasedExpression) evalNode(r Record, tableAlias string) (*Value, error) {
	return e.Expression.evalNode(r, tableAlias)
}

func (e *Expression) evalNode(r Record, tableAlias string) (*Value, error) {