DependencyContainer

Dependency Injection and Service Locator container registry.

This contains all the necessary information to initialize registered classes. Objects instantiated by the container are lazily loaded and initialized only on first use.

Provides the following decorators: register, abstract and autowire. Use register on factory functions and concrete classes which are to be injected from the container. Abstract classes are to be used as interfaces and will not be injected directly, rather concrete classes which implement them will be injected instead.

Use the autowire decorator on methods where dependency injection must be performed. To enable parameter injection use default values for parameters in conjunction with the wire method.

Note

Fastapi users MUST use = .wire() method without arguments when injecting dependencies.

Functions

__init__(parameter_bag)

Parameters:

Name	Type	Description	Default
parameter_bag	ParameterBag	ParameterBag instance holding parameter information.	required

abstract(klass)

Register a type as an interface.

This type cannot be initialized directly and one of the components implementing this will be injected instead.

autowire(fn)

Automatically inject resources from the container to the decorated methods.

Any arguments which the container does not know about will be ignored so that another decorator or framework can supply their values. This decorator can be used on both async and blocking methods.

• Classes will be automatically injected.
• Parameters need a value to be provided via .wire(param=) or .wire(expr=) using a default value.
• When injecting an interface for which there are multiple implementations you need to supply a qualifier via .wire(qualifier=) using a default value.

get(klass, qualifier=None)

Get an instance of the requested type.

Use this to locate services by their type but strongly prefer using injection instead.

Parameters:

Name	Type	Description	Default
qualifier	ContainerProxyQualifierValue	Qualifier for the class if it was registered with one.	None
klass	type[__T]	Class of the dependency already registered in the container.	required

Returns:

Type	Description
__T	An instance of the requested object. Always returns an existing instance when one is available.

register(obj=None, *, qualifier=None)

Register a dependency in the container.

Use @register without parameters on a class or with a single parameter @register(qualifier=name) to register this with a given name when there are multiple implementations of the interface this implements.

Use @register on a function to register that function as a factory method which produces an object that matches its return type.

The container stores all necessary metadata for this class and the underlying class remains unmodified.

register_all_in_module(module, pattern='*')

Register all modules inside a given module.

Useful when your components reside in one place, and you'd like to avoid having to @register each of them. Alternatively this can be used if you want to use the library without having to rely on decorators.

See Also: self.initialization_context to wire parameters without having to use a default value.

Parameters:

Name	Type	Description	Default
module	ModuleType	The package name to recursively search for classes.	required
pattern	str	A pattern that will be fed to fnmatch to determine if a class will be registered or not.	'*'