# Klassen als Abhängigkeiten { #classes-as-dependencies }

Bevor wir tiefer in das **Dependency Injection** System eintauchen, lassen Sie uns das vorherige Beispiel verbessern.

## Ein `dict` aus dem vorherigen Beispiel { #a-dict-from-the-previous-example }

So, a Python class is also a **callable**.

Then, in **FastAPI**, you could use a Python class as a dependency.

What FastAPI actually checks is that it is a "callable" (function, class or anything else) and the parameters defined.

If you pass a "callable" as a dependency in **FastAPI**, it will analyze the parameters for that "callable", and process them in the same way as the parameters for a *path operation function*. Including sub-dependencies.

# Classes como Dependências { #classes-as-dependencies }

Antes de nos aprofundarmos no sistema de **Injeção de Dependência**, vamos melhorar o exemplo anterior.

## `dict` do exemplo anterior { #a-dict-from-the-previous-example }

No exemplo anterior, nós retornávamos um `dict` da nossa dependência ("injetável"):

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

# Классы как зависимости { #classes-as-dependencies }

Прежде чем углубиться в систему **Внедрения Зависимостей**, давайте обновим предыдущий пример.

## `dict` из предыдущего примера { #a-dict-from-the-previous-example }

В предыдущем примере мы возвращали `dict` из нашей зависимости:

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

Но затем мы получаем `dict` в параметре `commons` *функции-обработчика пути*.

# Clases como dependencias { #classes-as-dependencies }

Antes de profundizar en el sistema de **Inyección de Dependencias**, vamos a mejorar el ejemplo anterior.

## Un `dict` del ejemplo anterior { #a-dict-from-the-previous-example }

En el ejemplo anterior, estábamos devolviendo un `dict` de nuestra dependencia ("dependable"):

{* ../../docs_src/dependencies/tutorial001_an_py310.py hl[9] *}

from .v2 import RequiredParam as RequiredParam
from .v2 import Undefined as Undefined
from .v2 import UndefinedType as UndefinedType
from .v2 import Url as Url
from .v2 import Validator as Validator
from .v2 import _regenerate_error_with_loc as _regenerate_error_with_loc
from .v2 import copy_field_info as copy_field_info
from .v2 import create_body_model as create_body_model

		register["g"] = x86.REGG
	}
	// Register prefix not used on this architecture.

	instructions := make(map[string]obj.As)
	for i, s := range obj.Anames {
		instructions[s] = obj.As(i)
	}
	for i, s := range x86.Anames {
		if obj.As(i) >= obj.A_ARCHSPECIFIC {
			instructions[s] = obj.As(i) + obj.ABaseAMD64
		}
	}
	// Annoying aliases.
	instructions["JA"] = x86.AJHI   /* alternate */

	}

	r = dryDB.Table("people as p").Table("user as u").Find(&User{}).Statement
	if !regexp.MustCompile("SELECT \\* FROM user as u WHERE .u.\\..deleted_at. IS NULL").MatchString(r.Statement.SQL.String()) {
		t.Errorf("Table with escape character, got %v", r.Statement.SQL.String())
	}

	r = dryDB.Table("people as p").Table("user").Find(&User{}).Statement

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[3] *}

## Declare `Header` parameters { #declare-header-parameters }

Then declare the header parameters using the same structure as with `Path`, `Query` and `Cookie`.

You can define the default value as well as all the extra validation or annotation parameters:

{* ../../docs_src/header_params/tutorial001_an_py310.py hl[9] *}

/// note | Technical Details

And you can also declare body parameters as optional, by setting the default to `None`:

{* ../../docs_src/body_multiple_params/tutorial001_an_py310.py hl[18:20] *}

/// note

Notice that, in this case, the `item` that would be taken from the body is optional. As it has a `None` default value.

///

## Multiple body parameters { #multiple-body-parameters }