factory pattern with lambda

Question

How would you create a factory based method using lambda?

function signature looks like this. Factory gets a string parameter and returns the instance.

class Foo:

    @abstractmethod
    def store(factory: Callable[[str], Bar])
       obj = factory("abc") # store or call to get instance


class Bar:
    def __init__(self):
        pass

How to call this method using lambda?

Foo.store(lambda k: Bar(k))

Error

Parameter 'factory' unfilled

Answer 1

Since store() is called on the class, not an instance, it needs to be declared as a static method.

class Foo:

    @staticmethod
    def store(factory: Callable[[str], Bar]):
        obj = factory("abc")  # store or call to get instance

Otherwise, it's expected to be called on an instance, and the first argument should be self, which receives the instance.

Also, obj is just a local variable. If you want this to persist, you need to use Foo.obj.