names.md

Names

If you specify a name in your binding, only parameters with the same name will use this binding. If no bindings with the same name are found, a binding without a name will be used as a fallback if available. You can use this to inject different objects for the same type.

from opyoid import Module, Injector


class MyClass1:
    def __init__(self, class_1_param: str, other_param: str):
        self.class_1_param = class_1_param
        self.other_param = other_param

class MyClass2:
    def __init__(self, class_2_param: str):
        self.class_2_param = class_2_param


class MyModule(Module):
    def configure(self) -> None:
        self.bind(MyClass1)
        self.bind(MyClass2)
        self.bind(str, to_instance="my_value_1", named="class_1_param")
        self.bind(str, to_instance="my_value_2", named="class_2_param")
        self.bind(str, to_instance="default_value")

injector = Injector([MyModule()])
instance_1 = injector.inject(MyClass1)
assert isinstance(instance_1, MyClass1)
assert instance_1.class_1_param == "my_value_1"
assert instance_1.other_param == "default_value"
instance_2 = injector.inject(MyClass2)
assert isinstance(instance_2, MyClass2)
assert instance_2.class_2_param == "my_value_2"

If you want to specify a different name, for example if multiple classes use the same type with the same name, you can use the @named_arg decorator. This will not change the signature of the constructor, only opyoid will detect the new name. Using this decorator will also prevent the unnamed binding to be used.

from opyoid import named_arg, Module, Injector


class MyClass1:
    @named_arg("my_param", "class_1_param")
    @named_arg("other_param", "class_1_other_param")
    def __init__(self, my_param: str, other_param: str = "fallback_value"):
        self.my_param = my_param
        self.other_param = other_param

class MyClass2:
    @named_arg("my_param", "class_2_param")
    def __init__(self, my_param: str):
        self.my_param = my_param


class MyModule(Module):
    def configure(self) -> None:
        self.bind(MyClass1)
        self.bind(MyClass2)
        self.bind(str, to_instance="my_value_1", named="class_1_param")
        self.bind(str, to_instance="my_value_2", named="class_2_param")
        self.bind(str, to_instance="default_value")

injector = Injector([MyModule()])
instance_1 = injector.inject(MyClass1)
assert isinstance(instance_1, MyClass1)
assert instance_1.my_param == "my_value_1"
assert instance_1.other_param == "fallback_value"
instance_2 = injector.inject(MyClass2)
assert isinstance(instance_2, MyClass2)
assert instance_2.my_param == "my_value_2"