root / snf-common / synnefo / lib / singleton / __init__.py @ d509e6da
History | View | Annotate | Download (2.5 kB)
1 | 19092a69 | Vangelis Koukis | # Copyright 2011-2012 GRNET S.A. All rights reserved.
|
---|---|---|---|
2 | 19092a69 | Vangelis Koukis | #
|
3 | 19092a69 | Vangelis Koukis | # Redistribution and use in source and binary forms, with or
|
4 | 19092a69 | Vangelis Koukis | # without modification, are permitted provided that the following
|
5 | 19092a69 | Vangelis Koukis | # conditions are met:
|
6 | 19092a69 | Vangelis Koukis | #
|
7 | 19092a69 | Vangelis Koukis | # 1. Redistributions of source code must retain the above
|
8 | 19092a69 | Vangelis Koukis | # copyright notice, this list of conditions and the following
|
9 | 19092a69 | Vangelis Koukis | # disclaimer.
|
10 | 19092a69 | Vangelis Koukis | #
|
11 | 19092a69 | Vangelis Koukis | # 2. Redistributions in binary form must reproduce the above
|
12 | 19092a69 | Vangelis Koukis | # copyright notice, this list of conditions and the following
|
13 | 19092a69 | Vangelis Koukis | # disclaimer in the documentation and/or other materials
|
14 | 19092a69 | Vangelis Koukis | # provided with the distribution.
|
15 | 19092a69 | Vangelis Koukis | #
|
16 | 19092a69 | Vangelis Koukis | # THIS SOFTWARE IS PROVIDED BY GRNET S.A. ``AS IS'' AND ANY EXPRESS
|
17 | 19092a69 | Vangelis Koukis | # OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
|
18 | 19092a69 | Vangelis Koukis | # WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
|
19 | 19092a69 | Vangelis Koukis | # PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL GRNET S.A OR
|
20 | 19092a69 | Vangelis Koukis | # CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
|
21 | 19092a69 | Vangelis Koukis | # SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
|
22 | 19092a69 | Vangelis Koukis | # LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
23 | 19092a69 | Vangelis Koukis | # USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
|
24 | 19092a69 | Vangelis Koukis | # AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
|
25 | 19092a69 | Vangelis Koukis | # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
|
26 | 19092a69 | Vangelis Koukis | # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
|
27 | 19092a69 | Vangelis Koukis | # POSSIBILITY OF SUCH DAMAGE.
|
28 | 19092a69 | Vangelis Koukis | #
|
29 | 19092a69 | Vangelis Koukis | # The views and conclusions contained in the software and
|
30 | 19092a69 | Vangelis Koukis | # documentation are those of the authors and should not be
|
31 | 19092a69 | Vangelis Koukis | # interpreted as representing official policies, either expressed
|
32 | 19092a69 | Vangelis Koukis | # or implied, of GRNET S.A.
|
33 | 19092a69 | Vangelis Koukis | |
34 | 19092a69 | Vangelis Koukis | |
35 | 19092a69 | Vangelis Koukis | class ArgBasedSingletonMeta(type): |
36 | 19092a69 | Vangelis Koukis | """Implement the Singleton pattern with a twist.
|
37 | 19092a69 | Vangelis Koukis |
|
38 | 19092a69 | Vangelis Koukis | Implement the Singleton pattern with a twist:
|
39 | 19092a69 | Vangelis Koukis | The uniqueness on the object is based on the class name,
|
40 | 19092a69 | Vangelis Koukis | plus the argument list (args and kwargs).
|
41 | 19092a69 | Vangelis Koukis |
|
42 | 19092a69 | Vangelis Koukis | Unique objects are store in the '_singles' class attribute.
|
43 | 19092a69 | Vangelis Koukis | A distinct _singles object is used per subclass.
|
44 | 19092a69 | Vangelis Koukis |
|
45 | 19092a69 | Vangelis Koukis | """
|
46 | 19092a69 | Vangelis Koukis | def __call__(cls, *args, **kwargs): |
47 | 19092a69 | Vangelis Koukis | kwlist = str([(k, kwargs[k]) for k in sorted(kwargs.keys())]) |
48 | 19092a69 | Vangelis Koukis | distinct = str((cls, args, kwlist))
|
49 | 19092a69 | Vangelis Koukis | |
50 | 19092a69 | Vangelis Koukis | # Allocate a new _singles attribute per subclass
|
51 | 19092a69 | Vangelis Koukis | if not hasattr(cls, "_singles_cls") or cls != cls._singles_cls: |
52 | 19092a69 | Vangelis Koukis | cls._singles = {} |
53 | 19092a69 | Vangelis Koukis | cls._singles_cls = cls |
54 | 19092a69 | Vangelis Koukis | |
55 | 19092a69 | Vangelis Koukis | if distinct not in cls._singles: |
56 | 19092a69 | Vangelis Koukis | obj = super(ArgBasedSingletonMeta, cls).__call__(*args, **kwargs)
|
57 | 19092a69 | Vangelis Koukis | cls._singles[distinct] = obj |
58 | 19092a69 | Vangelis Koukis | |
59 | 19092a69 | Vangelis Koukis | ret = cls._singles[distinct] |
60 | 19092a69 | Vangelis Koukis | |
61 | 19092a69 | Vangelis Koukis | return ret
|
62 | 74d988b0 | Christos Stavrakakis | |
63 | 19092a69 | Vangelis Koukis | |
64 | 19092a69 | Vangelis Koukis | class ArgBasedSingleton(object): |
65 | 19092a69 | Vangelis Koukis | __metaclass__ = ArgBasedSingletonMeta |