Sérgio Vale e Pace wrote:
template < typename T > struct auto_set { T & var; T val; auto_set ( T & var, T val ) :
auto_set(T & var,T val = T()): // allows one to just specify a variable to be auto-set back to its default value also
var ( var ), val ( val ) { }
// IMHO I thing it´s more often useful to use var own value to be restored later: auto_set(T& var) : var(var), val(var) { }
~ auto_set ( ) { var = val; } };
Perhaps. You might be interested to see why I originally wrote it though: virtual void create ( ) { if ( !s_inst && !creating ) { creating = true; auto_set < bool > reset ( creating, false ); s_inst = creator_inst.create ( ); } } virtual void destroy ( ) { if ( s_inst && !destroying ) { destroying = true; auto_set < bool > reset_d ( destroying, false ); auto_set < raw_pointer > reset_p ( s_inst, 0 ); creator_inst.destroy ( s_inst ); } } Basically, when create is called, the constructor of the singleton being created just might do something that would normally cause that singleton to be automatically created. I use a bool to remember that a creation is in progress, and auto_set makes sure that it gets turned off when the scope is exited. The same kind of thing is going on in destroy, but I also ensure that the pointer to the singleton gets reset to null after destruction is complete. -Jason