"""Standard Injector implementation."""
from typing import Mapping, Optional, Type
from .base import BaseProvider, BaseInjector, InjectionError, InjectType
from .provider import InstanceProvider, CachedProvider
from .settings import Settings
[docs]class Injector(BaseInjector):
"""Injector implementation with static and dynamic bindings."""
def __init__(
self, settings: Mapping[str, object] = None, *, enforce_typing: bool = True
):
"""Initialize an `Injector`."""
self.enforce_typing = enforce_typing
self._providers = {}
self._settings = Settings(settings)
@property
def settings(self) -> Settings:
"""Accessor for scope-specific settings."""
return self._settings
@settings.setter
def settings(self, settings: Settings):
"""Setter for scope-specific settings."""
self._settings = settings
[docs] def bind_instance(self, base_cls: Type[InjectType], instance: InjectType):
"""Add a static instance as a class binding."""
self._providers[base_cls] = InstanceProvider(instance)
[docs] def bind_provider(
self, base_cls: Type[InjectType], provider: BaseProvider, *, cache: bool = False
):
"""Add a dynamic instance resolver as a class binding."""
if not provider:
raise ValueError("Class provider binding must be non-empty")
if cache and not isinstance(provider, CachedProvider):
provider = CachedProvider(provider)
self._providers[base_cls] = provider
[docs] def clear_binding(self, base_cls: Type[InjectType]):
"""Remove a previously-added binding."""
if base_cls in self._providers:
del self._providers[base_cls]
[docs] def get_provider(self, base_cls: Type[InjectType]):
"""Find the provider associated with a class binding."""
return self._providers.get(base_cls)
[docs] def inject_or(
self,
base_cls: Type[InjectType],
settings: Mapping[str, object] = None,
default: Optional[InjectType] = None,
) -> Optional[InjectType]:
"""Get the provided instance of a given class identifier or default if not found.
Args:
base_cls: The base class to retrieve an instance of
settings: An optional dict providing configuration to the provider
default: default return value if no instance is found
Returns:
An instance of the base class, or None
"""
if not base_cls:
raise InjectionError("No base class provided for lookup")
provider = self._providers.get(base_cls)
if settings:
ext_settings = self.settings.extend(settings)
else:
ext_settings = self.settings
if provider:
result = provider.provide(ext_settings, self)
else:
result = None
if result and not isinstance(result, base_cls) and self.enforce_typing:
raise InjectionError(
"Provided instance does not implement the base class: {}".format(
base_cls.__name__
)
)
return result if result is not None else default
[docs] def inject(
self,
base_cls: Type[InjectType],
settings: Mapping[str, object] = None,
) -> InjectType:
"""Get the provided instance of a given class identifier.
Args:
cls: The base class to retrieve an instance of
params: An optional dict providing configuration to the provider
Returns:
An instance of the base class, or None
"""
result = self.inject_or(base_cls, settings)
if result is None:
raise InjectionError(
"No instance provided for class: {}".format(base_cls.__name__)
)
return result
[docs] def copy(self) -> BaseInjector:
"""Produce a copy of the injector instance."""
result = Injector(self.settings)
result.enforce_typing = self.enforce_typing
result._providers = self._providers.copy()
return result
def __repr__(self) -> str:
"""Provide a human readable representation of this object."""
return f"<{self.__class__.__name__}>"