STL vector class

[djames11]

In my project, we are currently loading a list of movies into an array. We have to change the program to use a vector. I added my vector,

vector<Movie> movies2;

which correctly creates and loads the movies in.

while(!iS.eof()) {
movies[movieCnt++] = Movie(s);
Movie o = Movie(s);
movies2.push_back(o);
getline(iS, s);
}

but now I am trying to create an iterator to go traverse through the list when I need to retrieve a movie. I have set it up like all the examples I know but it keeps complaining.

vector<Movie>::iterator p; (in my my header class)

const Movie * Movies::getMovie(string mc, int& mn) const {
//vector<Movie>::iterator p;
p = movies2.begin();
if(mc.length()==0)
return NULL; // not found
else {
string mcP = myToLower(mc);
int ndx=0;
for(;ndx<movieCnt &&
(myToLower(p[ndx].getTitle()).find(mcP)==
string::npos);ndx++);
mn = ndx<movieCnt?ndx+1:0;
return ndx<movieCnt?&p[ndx]:NULL;
}
}

Does anyone see what I could possibly be missing? This is my first time working with vectors and I am lost.

[Texan40]

If you are bothering to use an iterator then you should probably use it to iterate through the vector:

const Movie * Movies::getMovie(string mc, int& mn) const
{
  if(mc.size())
  {
    string mcP = myToLower(mc);
    for(vector<Movie>::iterator p = movies2.begin(); p != movies2.end(); ++p)
    {
      if((p->getTitle()).find(mcP) != string::npos) // found substring in title
      {
        mn = (p - movies2.begin()); // can only do this on random access iterators
        return p; // not sure if we need a cast here or something like `return static_cast<const Movie*>(p); ??
      }
    }
  }
  return NULL;
}

EDIT: forgot to set mn (why do you need the numeric index if you are returning a pointer to the object?)

[djames11]

That makes sense. The numeric indexing was a way my teacher did it but we are not limited to do it that way. Thanks for the help. I am going to adjust my code with your suggestion and see how it works. Thanks again.

[IceThatJaw]

Yea, the great thing about vectors is that you don't need to use an iterator. However, if you are going to be changing the dimensions of the vector in a loop than you should use an iterator. You can typedef them to make it more readable if you are declaring them a lot.

But you can actually just traverse it like an array if you'd like.

vector<int> v;

for (int i = 0; i < v.size(); i++)
     cout << v[i] << endl;