# Dependências com yield

O FastAPI possui suporte para dependências que realizam <abbr title='também chamados de "código de saída", "código de cleanup", "código de teardown", "código de finalização", "código de saída para gerenciador de contextos", etc.'>alguns passos extras ao finalizar</abbr>.

Para fazer isso, utilize `yield` em vez de `return`, e escreva os passos extras (código) depois.

/// tip | "Dica"

Garanta que `yield` é utilizado apenas uma vez.

			if len(gotFields) != len(test.expectedFields) {
				t.Errorf("Expected keys %d, found %d", len(test.expectedFields), len(gotFields))
			}
			found := true
			for _, field := range gotFields {
				_, ok := test.expectedFields[field]
				found = found && ok
			}
			if !found {
				t.Errorf("Expected %s, got %s", test.expectedFields, gotFields)
			}
		})
	}
}

			// incorrectly believed that the old GNU format had a prefix field.
			// This is wrong and leads to an output file that mangles the
			// atime and ctime fields, which are often left unused.
			//
			// In order to continue reading tar files created by former, buggy
			// versions of Go, we skeptically parse the atime and ctime fields.
			// If we are unable to parse them and the prefix field looks like

func (z *BaseOptions) DecodeMsg(dc *msgp.Reader) (err error) {
	var field []byte
	_ = field
	var zb0001 uint32
	zb0001, err = dc.ReadMapHeader()
	if err != nil {
		err = msgp.WrapError(err)
		return
	}
	for zb0001 > 0 {
		zb0001--
		field, err = dc.ReadMapKeyPtr()
		if err != nil {
			err = msgp.WrapError(err)
			return
		}
		switch msgp.UnsafeString(field) {
		default:
			err = dc.Skip()
			if err != nil {

  // API. This field is deprecated, and will be removed when the v1beta1
  // API is removed (no sooner than kubernetes v1.24).  While this field can
  // hold values, it is not writable through the v1 API, and any attempts to
  // write to it will be silently ignored. Topology information can be found
  // in the zone and nodeName fields instead.
  // +optional
  map<string, string> deprecatedTopology = 5;

//go:generate msgp -file $GOFILE

// BucketMetadata contains bucket metadata.
// When adding/removing fields, regenerate the marshal code using the go generate above.
// Only changing meaning of fields requires a version bump.
// bucketMetadataFormat refers to the format.
// bucketMetadataVersion can be used to track a rolling upgrade of a field.
type BucketMetadata struct {
	Name                        string
	Created                     time.Time

      - "https://server4-pool1:9000/mnt/disk{1...4}/"
    set-drive-count: 4 # Advanced option, must be used under guidance from MinIO team.
```

### Things to know

- Fields such as `version` and `pools` are mandatory, however all other fields are optional.
- Each pool expects a minimum of 2 nodes per pool, and unique non-repeating hosts for each argument.

		"PFAndESI":                  "pf_and_esi",
		"AbcAndJkl":                 "abc_and_jkl",
		"EmployeeID":                "employee_id",
		"SKU_ID":                    "sku_id",
		"FieldX":                    "field_x",
		"HTTPAndSMTP":               "http_and_smtp",
		"HTTPServerHandlerForURLID": "http_server_handler_for_url_id",
		"UUID":                      "uuid",
		"HTTPURL":                   "http_url",

	TCPOptions    TCPOptions    // all the configurable TCP conn specific configurable options.
	listenerMutex sync.Mutex    // to guard 'listener' field.
	listener      *httpListener // HTTP listener for all 'Addrs' field.
	inShutdown    uint32        // indicates whether the server is in shutdown or not
	requestCount  int32         // counter holds no. of request in progress.
}

**FastAPI** はこれを実現するために内部的に使用しています。

///

## `yield`と`HTTPException`を持つ依存関係

`yield`と例外をキャッチする`try`ブロックを持つことができる依存関係を使用することができることがわかりました。

`yield`の後の終了コードで`HTTPException`などを発生させたくなるかもしれません。しかし**それはうまくいきません**

`yield`を持つ依存関係の終了コードは[例外ハンドラ](../handling-errors.md#_4){.internal-link target=_blank}の*後に*実行されます。依存関係によって投げられた例外を終了コード（`yield`の後）でキャッチするものはなにもありません。