架构x86_64的未定义符号与c++的链接错误

我有一个程序，用户在其中输入飞机的操作。用户可以选择任意多的操作(保持，直线，着陆等)，因为他/她想。用户可通过操作5计算所需的进油量。

我将抽象工厂设计模式应用到系统中，如下所示:

FlightModeInterface.h

class FlightModeInterface{
protected:
float time, fuel_rate, start, end, pace, distance;
float total;
public:
    enum FLIGHT_MODES{
        HOLDING,
        RAISING,
        LANDING,
        STRAIGHT
    };
    FlightModeInterface();
    virtual ~FlightModeInterface(){ }
    virtual float calcFuel(float, float, float,
              float, float, float) = 0;
    static FlightModeInterface* createFactory(FLIGHT_MODES);
};

FlightModeFactory.cpp

#include "FlightModeInterface.h"
#include "Holding.h"
#include "Landing.h"
#include "Raising.h"
#include "Straight.h"
class FlightModeFactory{
protected:
    float time, fuel_rate, start, end, pace, distance;
    float total;
public:
    static FlightModeInterface* createFactory(FlightModeInterface::FLIGHT_MODES mode){
        switch (mode) {
            case FlightModeInterface::HOLDING:
                return new Holding();
            case FlightModeInterface::LANDING:
                return new Landing();
            case FlightModeInterface::RAISING:
                return new Raising();
            case FlightModeInterface::STRAIGHT:
                return new Straight();
        }
        throw "invalid flight mode.";
    }
};

CalculateFuel.cpp

#include <iostream>
#include <stdio.h>
#include "FlightModeInterface.h"
using namespace std;

int main(){
    char op = 's';
    float time=0, fuel_rate=0, start=0, end=0, pace=0, distance=0;
    float total = 0;
    FlightModeInterface *factory;
    while(op != 'x') {
        float hold_result, raise_result, land_result, str_result;
        cout << "Please select an operation: " << endl;
        cout << "1 ---> Holding flight" << endl;
        cout << "2 ---> Raising" << endl;
        cout << "3 ---> Landing " << endl;
        cout << "4 ---> Straight " << endl;
        cout << "5 ---> Calculate total fuel consumption" << endl;
        cout << "x ---> Exit " << endl;
        cin >> op;
        switch(op){
        case '1':
            cout << "Holding time (minutes): ";
            cin >> time;
            cout << "Fuel rate (kg/sec): ";
            cin >> fuel_rate;
            factory = FlightModeInterface::createFactory(FlightModeInterface::HOLDING);
            hold_result = factory -> calcFuel(time, fuel_rate, 0, 0, 0, 0);
            total += hold_result;
            break;
        case '5':
            cout <<"Total fuel requirement: "<< total << " kg"<< endl;
            total = 0;
            break;
        case 'x':
            return 0;
        default:
            continue;
        }
    }
    return 0;
}

当我运行CalculateFuel.cpp时，我遇到了这个错误(我使用Eclipse Builder在MAC上构建代码):

23:46:08 **** Build of configuration Debug for project CalculateFuel ****
make all 
Building file: ../src/CalculateFuel.cpp
Invoking: GCC C++ Compiler
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/CalculateFuel.d" -MT"src/CalculateFuel.d" -o "src/CalculateFuel.o" "../src/CalculateFuel.cpp"
Finished building: ../src/CalculateFuel.cpp
Building file: ../src/FlightModeFactory.cpp
Invoking: GCC C++ Compiler
g++ -O0 -g3 -Wall -c -fmessage-length=0 -MMD -MP -MF"src/FlightModeFactory.d" -MT"src/FlightModeFactory.d" -o "src/FlightModeFactory.o" "../src/FlightModeFactory.cpp"
Finished building: ../src/FlightModeFactory.cpp
Building target: CalculateFuel
Invoking: MacOS X C++ Linker
g++  -o "CalculateFuel"  ./src/CalculateFuel.o ./src/FlightModeFactory.o   
Undefined symbols for architecture x86_64:
  "FlightModeInterface::createFactory(FlightModeInterface::FLIGHT_MODES)", referenced from:
      _main in CalculateFuel.o
ld: symbol(s) not found for architecture x86_64
clang: error: linker command failed with exit code 1 (use -v to see invocation)
make: *** [CalculateFuel] Error 1

对于如何解决这个问题有什么想法吗?