# Dependencies with yield { #dependencies-with-yield }

FastAPI supports dependencies that do some <abbr title='sometimes also called "exit code", "cleanup code", "teardown code", "closing code", "context manager exit code", etc.'>extra steps after finishing</abbr>.

To do this, use `yield` instead of `return`, and write the extra steps (code) after.

/// tip

Make sure to use `yield` one single time per dependency.

///

/// note | Technical Details

			}
			if !yield(line[:len(line):len(line)]) {
				return
			}
		}
	}
}

// splitSeq is SplitSeq or SplitAfterSeq, configured by how many
// bytes of sep to include in the results (none or all).
func splitSeq(s, sep []byte, sepSave int) iter.Seq[[]byte] {
	return func(yield func([]byte) bool) {
		if len(sep) == 0 {
			for len(s) > 0 {
				_, size := utf8.DecodeRune(s)
				if !yield(s[:size:size]) {
					return

새로운 버전을 시작해야 하거나, 그냥 실행을 멈추고 싶을 수도 있습니다. 🤷

///

### Lifespan 함수

먼저 주목할 점은, `yield`를 사용하여 비동기 함수(async function)를 정의하고 있다는 것입니다. 이는 `yield`를 사용한 의존성과 매우 유사합니다.

{* ../../docs_src/events/tutorial003.py hl[14:19] *}

함수의 첫 번째 부분, 즉 `yield` 이전의 코드는 애플리케이션이 시작되기 **전에** 실행됩니다.

그리고 `yield` 이후의 부분은 애플리케이션이 완료된 후 **나중에** 실행됩니다.

### 비동기 컨텍스트 매니저

함수를 확인해보면, `@asynccontextmanager`로 장식되어 있습니다.

{* ../../docs_src/events/tutorial003.py hl[14:19] *}

The first part of the function, before the `yield`, will be executed **before** the application starts.

And the part after the `yield` will be executed **after** the application has finished.

### Async Context Manager { #async-context-manager }

                    yield webConfigService.getWebConfig(id).get();
                }
                case FILE -> {
                    final FileConfigService fileConfigService = ComponentUtil.getComponent(FileConfigService.class);
                    yield fileConfigService.getFileConfig(id).get();
                }
                case DATA -> {

    corruptor()

    return client.newCall(request).execute()
  }

  /**
   * @param delta the offset from the current date to use. Negative values yield dates in the past;
   *     positive values yield dates in the future.
   */
  private fun formatDate(
    delta: Long,
    timeUnit: TimeUnit,
  ): String? = formatDate(Date(System.currentTimeMillis() + timeUnit.toMillis(delta)))

          taskRunner: TaskRunner,
          nanos: Long,
        ) {
          taskRunner.assertLockHeld()
          check(waitingCoordinatorTask == null)
          if (nanos == 0L) return

          // Yield until notified, interrupted, or the duration elapses.
          val waitUntil = nanoTime + nanos
          val self = currentTask
          waitingCoordinatorTask = self
          waitingCoordinatorNotified = false

                interruptee.interrupt();
                Thread.yield();
              }
            }
          });
      this.shutdown = shutdown;
      start();
    }

    @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait.
    void shutdown() {
      shutdown.set(true);
      while (this.isAlive()) {
        Thread.yield();
      }
    }
  }

                        tree.acquire();
                        successCount.incrementAndGet();

                        // Small delay to increase chance of race conditions
                        Thread.yield();
                    }
                } catch (Exception e) {
                    exceptions.add(e);
                } finally {
                    endLatch.countDown();
                }
            });

                interruptee.interrupt();
                Thread.yield();
              }
            }
          });
      this.shutdown = shutdown;
      start();
    }

    @SuppressWarnings("ThreadPriorityCheck") // TODO: b/175898629 - Consider onSpinWait.
    void shutdown() {
      shutdown.set(true);
      while (this.isAlive()) {
        Thread.yield();
      }
    }
  }