将迭代器传递给函数

Question

I have the following code which is being used to find the weakest target out of a vector which is a vector containing a pointer to all the active units. I am trying to create an iterator that will go through each unit and pass it to another function called can_attack(Unit &u, Unit &v) which takes two units and measures if they are close enough to each other to attack.

On compilation I am getting the following error "error: reference to type 'const Unit' could not bind to an lvalue of type 'Unit *const'". I understand that I am passing in the wrong type of variable but am unsure how to turn the iterator into a const Unit. Thanks for any help

void World::enemies_within_attack_range(const Unit &u,
                                    vector<Unit*> &targets) const
{
  targets.clear();
  vector<Unit*>::const_iterator it=units.begin();
  for(it;it!=units.end();it++){
    if((*it)->team != u.team){
        if(can_attack(u,(*it))){
            targets.push_back(*it);
        }
     }
  }

}

Answer 1

The problem is in can_attack call and the parameter const Unit &u. The call has to be corrected as songyuanyao mentioned: can_attack(u,*(*it)). But this is not the only problem. There are three options:

1. instead of const Unit &u, declare u as Unit & u;
2. instead of can_attack(Unit &u, Unit &v), declare it as can_attack(const Unit &u, Unit &v) if possible;
3. (this is probably the worst option) use call can_attack(const_cast < Unit& > (u),*(*it)).

The choice is yours.