Source code for pytiger.utils.decorators

# -*- coding: utf-8 -*-

# class cached_property is
# Copyright (c) Django Software Foundation and individual contributors.
# All rights reserved.
# License: BSD
# Source: django.utils.functional.cached_property




class cached_property(object):
    """
    .. versionadded:: 1.0.0

    Decorator that converts a method with a single self argument into a
    property cached on the instance.

    Optional ``name`` argument allows you to make cached properties of other
    methods. (e.g.  url = cached_property(get_absolute_url, name='url') )
    """
    # This entire class was obtained from Django (django/util/functional.py),
    # which is licensed under a 3-clause BSD license.
    # Copyright (c) Django Software Foundation and individual contributors.
    def __init__(self, func, name=None):
        self.func = func
        self.__doc__ = getattr(func, '__doc__')
        self.name = name or func.__name__

    def __get__(self, instance, type=None):
        if instance is None:
            return self
        res = instance.__dict__[self.name] = self.func(instance)
        return res





class singleton(object):
    """
    .. versionadded:: 1.1

    Decorator that ensures objects of a class are singleton,
    i.e. there is only one such object in existance.

    The first object of a class decorated with ``singleton`` is
    instantiated as normal; for all others the first object is
    returned instead.

    Example:

    >>> @singleton
    ... class TestSingletonObject():
    ...   def __init__(self, test_string=""):
    ...     self.test_string = test_string
    ...
    >>> A = TestSingletonObject("my test string")
    >>> B = TestSingletonObject("otherstring")
    >>> assert(B.test_string=="my test string")
    >>> assert(A is B)
    """
    def __init__(self, klass):
        self.klass = klass
        self.instance = None

    def __call__(self, *args, **kwds):
        if self.instance is None:
            self.instance = self.klass(*args, **kwds)
        return self.instance