Can't get ifstream to work in C++

Hi,
I'm trying to read a text file in a C++ program using an ifstream object but it keeps saying that it can't open the file. Here's a partial version of the code i'm using. Can anyone tell me why it's not reading the file? Am I missing a library or some other important part? The text file is in the same folder as my Xcode project file.

#include <vector>
#include <fstream>
#include <iostream>
#include <string>

#define FILE_IN "Pool LogData.txt"

using namespace std;


bool ReadFile(vector<string> & rvMonthYr, vector<int> & rvRecSwim,
vector<int> & rvLapSwim, vector<int> & rvLessons)
{
ifstream input;
input.open(FILE_IN);

//check that the file is open

if(!input)
{
cout << "\nSorry, there was a problem opening the file.";
return false;
}