Re: [boost] [review] Fast track review of Boost.Utility/Singletonbegins today

From: Johan Nilsson (r.johan.nilsson_at_[hidden])
Date: 2008-01-16 02:29:34

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