27e751f8   
   From: daniel.kruegler@googlemail.com   
      
   On 2012-01-18 21:12, kelvSYC wrote:   
   > Suppose I have this wrapper:   
   >   
   > template   
   > class ContainerWrapper {   
   >     Container container;   
   > public:   
   >     typedef Key key_type;   
   > protected:   
   >     virtual const typename Container::key_type&  mapKey(const key_type&   
   > key) = 0;   
   > };   
      
   It is important to realize that the design of Containerwrapper is the cause of   
   the problems in your derived classes and templates. For the moment I assume,   
   that ContainerWrapper is not intended to be specialized, but you should keep   
   this possibility in    
   mind. So:   
      
   a) either don't "imprint" references as return type of Container   
   rapper::mapKey;   
      
   b) or specialize ContainerWrapper for types that don't work well with the   
   reference-based approach;   
      
   c) or introduce a trait that allows to be more flexible when meapping between   
   template parameter Key and the return type of mapKey.   
      
   HTH & Greetings from Bremen,   
      
   Daniel Krügler   
      
      
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