# 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

{* ../../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 -> {

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

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

        case TIME_1601_NANOS_64BE -> {
            t = (date.getTime() + MILLISECONDS_BETWEEN_1970_AND_1601) * 10000L;
            yield enc_uint64be(t, dst, di);
        }
        case TIME_1601_NANOS_64LE -> {
            t = (date.getTime() + MILLISECONDS_BETWEEN_1970_AND_1601) * 10000L;
            yield enc_uint64le(t, dst, di);
        }
        case TIME_1970_MILLIS_64BE -> enc_uint64be(date.getTime(), dst, di);

            // Set private fields: status on SmbComTransactionResponse and available on TransPeekNamedPipeResponse
            Field statusField = jcifs.internal.smb1.trans.SmbComTransactionResponse.class.getDeclaredField("status");
            statusField.setAccessible(true);
            statusField.setInt(resp, status);
            Field availField = TransPeekNamedPipeResponse.class.getDeclaredField("available");
            availField.setAccessible(true);

            t = (date.getTime() + SmbConstants.MILLISECONDS_BETWEEN_1970_AND_1601) * 10000L;
            yield enc_uint64be(t, dst, di);
        }
        case TIME_1601_NANOS_64LE -> {
            t = (date.getTime() + SmbConstants.MILLISECONDS_BETWEEN_1970_AND_1601) * 10000L;
            yield enc_uint64le(t, dst, di);
        }
        case TIME_1970_MILLIS_64BE -> enc_uint64be(date.getTime(), dst, di);

1. This is the generator function. It's a "generator function" because it contains `yield` statements inside.
2. By using a `with` block, we make sure that the file-like object is closed after the generator function is done. So, after it finishes sending the response.
3. This `yield from` tells the function to iterate over that thing named `file_like`. And then, for each part iterated, yield that part as coming from this generator function (`iterfile`).

                        "timed out waiting for other threads to block"
                            + " synchronizing on supplier"));
                break;
              }
              Thread.yield();
            }
            count.getAndIncrement();
            return Boolean.TRUE;
          }
        };

    Supplier<Boolean> memoizedSupplier = memoizer.apply(supplier);