xcode4.3 — ошибка компоновщика C ++ в Xcode для статического метода

Я уверен, что это просто до мозга костей, но я просто не вижу этого. Я получаю следующую ошибку компоновщика в C ++ Xcode.

Undefined symbols for architecture x86_64:
"Random::NextInt(int, int)", referenced from:
Helpers::MakeData(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, int) in Helpers.o

Помощники :: MakeData

#include "Helpers.h"#include "Random.h"
void Helpers::MakeData(string dataFile, int numLines)
{
vector<double> weights = { -0.1, 0.2, -0.3, 0.4, -0.5,
0.6, -0.7, 0.8, -0.9, 1.0,
-1.1, 1.2, -1.3, 1.4, -1.5,
1.6, -1.7, 1.8, -1.9, 2.0,
-0.5, 0.6, -0.7, 0.8, -0.9,
1.5, -1.4, 1.3,
-1.2, 1.1, -1.0,
0.9, -0.8, 0.7,
-0.6, 0.5, -0.4,
0.3, -0.2, 0.1,
0.1, -0.3, 0.6 };

NeuralNetwork * nn = new NeuralNetwork(4, 5, 3);
nn->SetWeights(weights);
ofstream myFile;
myFile.open(dataFile);
for (int i = 0; i < numLines; ++i)
{
vector<double> inputs;
for (int j = 0; j < inputs.size(); ++j)
inputs[j] = Random::NextInt(10, 1);

vector<double> outputs = nn->ComputeOutputs(inputs);

string color = "";
int idx = Helpers::IndexOfLargest(outputs);
if (idx == 0) { color = "red"; }
else if (idx == 1) { color = "green"; }
else if (idx == 2) { color = "blue"; }

myFile << inputs[0] << " " << inputs[1] << " " << inputs[2] << " " << inputs[3] <<      " " << color;
}
myFile.close();
} // MakeData

Random.h

#ifndef __NeuralClassificationProgram__Random__
#define __NeuralClassificationProgram__Random__

#include <iostream>
class Random{

public:
static double NextDouble();
static int NextInt(int high, int low);
};

#endif /* defined(__NeuralClassificationProgram__Random__) */

Random.cpp

#include "Random.h"#include <time.h>
#include <stdlib.h>

double NextDouble()
{
double rnd;
srand(static_cast<unsigned int>(time(NULL)));
rnd = rand() % 1+0;
return rnd;
}

int NextInt(int high, int low)
{
int rnd;
srand(static_cast<unsigned int>(time(NULL)));
rnd = rand() % high + low;
return rnd;
}