engforge.patterns.Singleton

class Singleton(decorated)

Bases: object

A non-thread-safe helper class to ease implementing singletons. This should be used as a decorator – not a metaclass – to the class that should be a singleton.

The decorated class can define one __init__ function that takes only the self argument. Also, the decorated class cannot be inherited from. Other than that, there are no restrictions that apply to the decorated class.

To get the singleton instance, use the instance method. Trying to use __call__ will result in a TypeError being raised.

Methods

instance

Returns the singleton instance.

__call__()

Call self as a function.

instance(*args, **kwargs)

Returns the singleton instance. Upon its first call, it creates a new instance of the decorated class and calls its __init__ method. On all subsequent calls, the already created instance is returned.