向量类型为Struct的向量迭代器错误

Question

I'm trying to use a vector iterator to print out all of the elements in a vector. I've looked up similar questions but the solutions posted don't seem to be working for me. Here's the code:

void printPerms()
{
   for(vector<process>::iterator it = allProcesses.begin(); it != allProcesses.end(); it++)
   {
      for(int i = 0; i < numResourceTypes; i++)
      {
         cout << (static_cast<process*>(*it).need) << (static_cast<process>(*it)).allocated <<endl;
      }
   }
}

And the errors I am getting, which I don't know how to fix:

error C2440: 'static_cast' : cannot convert from 'process' to 'process *' No user
defined-conversion operator available that can perform this conversion, or the operator
cannot be called

error C2228: left of '.need' must have class/struct/union

Answer 1

Try...

void printPerms()
{
   for(vector<process>::iterator it = allProcesses.begin(); it != allProcesses.end(); it++)
   {
      for(int i = 0; i < numResourceTypes; i++)
      {
         cout << it->need << it->allocated << endl;
      }
   }
}

I don't know what exactly is going wrong, nor do I see why you need to use static_cast , however you should be able to access those member variables regardless using the -> operator.

De-referencing an iterator gives you its value (in this case, the process ), with no need for a cast.

Answer 2

The problem is that *it is of type process , you might try getting its address before casting by changing

(static_cast<process*>(*it).need)

to

((static_cast<process*>(&(*it)))->need)

However, it might be simpler to do it->need

By the way, if you are just printing (and not modifying the vector contents), then it is recommended to use const_iterator instead of iterator .