vector full of pointers

[A10]

If you have a vector containing pointers, how do you get another pointer to point where one of the pointers in a vector is pointing.

If what I said is hard to understand then here's the basic idea of what i want to accomplish
(not actual code from a program)

#include <vector>
#include <anyThingElseRequired>
using std::whateverComesFromTheStdNamespace;
...

vector<someObject*> v;      //vector full of pointers to someObject?
someObject *phead;            //pointer to someObject

v.put_back(phead);              //no trouble here

someObject *pnext;             //pointer to someObject

pnext = v[0];                        //cannot convert `std::vector<someObject*,             
                                             //std::allocator<someObject*> >' to `someObject*' in 
                                             //assignment

How do i get pnext to point to the same object that the pointer stored at v[0] is pointing to?

-Thank you for your patience

[Daved]

That code should work. Are you sure you used v[0] instead of v? Are you sure v is a vector<someObject*> and not a vector<vector<someObject*> >?

Copying and pasting the actual code that does each thing you typed out would make it easier to spot the error rather than seeing typos.

[A10]

My compiler devC++ seems to think its a"std::vector<agent*, std::allocator<agent*> >"
I'm just glanced at a vector tutorial page five minutes ago for the first time so I can't spot any error though it should be pretty obvious

Yes I did use v[0]. I'm thinking I've messed up the function arguments heres the actual code

//...heres where the function vector2Agent is called
     vector <agent*> parray;
     agent2Vector(parray, phead);
//...


agent *vector2Agent(vector<agent*> *parray, agent *phead) //i think the problem is here
{
      phead = parray[0];                                    //doesn't like this
      agent *pnext = phead;
      for(int x = 1; x < agent::listLength; x++)
              {
                  pnext->setNextAgent(parray[x]); //or this
                  pnext = pnext->getNextAgent();
              }      
      
}


/*actual compiler errors:
In function `agent* vector2Agent(std::vector<agent*, std::allocator<agent*> >*, agent*)': 

no matching function for call to `agent::setNextAgent(std::vector<agent*, std::allocator<agent*> >&)' 
*/

-Thanks for your help

[laserlight]

Indeed, you are passing a pointer to the vector as an argument. Hence, parray[0] is a vector. From what I see, you really want to pass a reference to the vector instead. You may also want to pass a reference to agent* if you really want the effects of phead's modification to extend to the caller.

[Daved]

>> heres where the function vector2Agent is called
Actually, it's calling agent2Vector, but I think we see what the problem is in this particular code. The error message you posted in the first post shouldn't be happening here, though.

BTW, vector <agent*> is kind of shorthand for the actual class that you are using. In this case, the compiler refers to the actual class as std::vector<agent*, std::allocator<agent*>, but you can pretty much ignore that and think of it as saying vector <agent*> whenever you see std::vector<agent*, std::allocator<agent*> in the error message. The allocator part is just a default parameter tha t advanced users set for memory management. Normal vector users ignore it and let the default allocator do the work.

[A10]

Indeed, you are passing a pointer to the vector as an argument. Hence, parray[0] is a vector. From what I see, you really want to pass a reference to the vector instead. You may also want to pass a reference to agent* if you really want the effects of phead's modification to extend to the caller.

That did exactly what I wanted, thank you

Actually, it's calling agent2Vector, but I think we see what the problem is in this particular code. The error message you posted in the first post shouldn't be happening here, though.

opps, yeah I didn't notice I copied the wrong one


The error msg from the first post was happening in here, I forgot to copy it. That msg went away after passing the vector and pointer by reference.

-Thank You