Source code for galaxy.di

"""Dependency injection framework for Galaxy-type apps."""
from typing import (
    Optional,
    Type,
    TypeVar,
)

from lagom import Container as LagomContainer
from lagom.exceptions import UnresolvableType

T = TypeVar("T")


[docs]class Container(LagomContainer): """Abstraction around lagom to provide a dependency injection context. Abstractions used by Galaxy should come through this interface so we can swap out the backend as needed. For instance https://punq.readthedocs.io/en/latest/ containers look very nice and would allow us to also inject by name (e.g. for config variables for instance). """ def _register_singleton(self, dep_type: Type[T], instance: Optional[T] = None) -> T: if instance is None: # create an instance from the context and register it as a singleton instance = self[dep_type] self[dep_type] = instance return self[dep_type]
[docs] def resolve_or_none(self, dep_type: Type[T]) -> Optional[T]: """Resolve the dependent type or just return None. If resolution is impossible assume caller has a backup plan for constructing the desired object. Used to construct controllers that may or may not be resolvable (some have upgraded but legacy framework still works). """ try: return self[dep_type] except UnresolvableType: return None