On 2008-08-14 12:44, Pascal J. Bourguignon wrote:
Oliver Graeser <graeser@phy.cuhk.edu.hk> writes:
Hi All,
I'm coming from Java to C++ and this is one of the very last problems
I have so far... In Java, if I have, say, a class SISNode that extends
NetworkNode, I can have a function that returns a NetworkNode but I
can assure the compiler that it is in fact a SISNode and therefore
call the method getStatus() that only a SISNode has. Like
SISnode s,t;
NetworkNode n;
n =t;
n.getStatus();//won't work
s= (SISNode) n;
s.getStatus(); //will work
No it won't.
...
...
I'm now looking for some way to do this in C++. I do agent-based
network simulations, and I want to derive all kinds of agents from a
generic network node type. This network node is supposed to store his
neighbours in a std::list<GenericNetworkNode> list. Now in the derived
classes I can obtain the neighbours, but I cannot call their methods
unless they were already declared in the GenericNetworkNode
declaration.
Anybody knows how to solve this problem? A hint in the right direction
(keyword) would be more than enough....
This is not possible, with what you wrote above and the assumed
declarations. You must realise that when you run n=t; you lose all
the information specific to a SISNode. There is no way to build it
back.
That's why I consider that C++ objects should always be allocated
dynamically and referend thru a pointer.
If you had written:
class SISNode:public NetworkNode {...};
SISNode* s=new SISNode();
NetworkNode* n=s;
then you could write:
SISNode* nAsSISNode=dynamic_cast<SISNode*>n;
if(nAsSISNode!=0){ nAsSISNode->getStatus(); }
can then use std::list<GenericNetworkNode*> to store them. Though it