16 Jan
2008
16 Jan
'08
7:29 a.m.
Pierre-Jules Tremblay wrote: [snip]
My biggest problem with this design is that it is unsuitable for library writers: types derived from typical singleton class designs, including boost::singleton and friends under review, invariably give rise to untestable code. To make a singleton's client code testable involves exposing some kind of overridable factory so that the singletonized type can be replaced with a test mockup. So far I have found this to be a hard problem to solve in general.
Did you notice that it is possible to use multiple inheritance? This way you can implement and test your domain-specific logic as a "normal" class, and then just expose a singleton of that specific type using e.g. boost::singleton<>. / Johan