矢量的未定義參考

Question

我在使用矢量時收到未定義的參考。

以下是錯誤：

/tmp/ccYnTr05.o: In function `TourManager::addCity(City)': 
tsp.cpp:(.text._ZN11TourManager7addCityE4City[TourManager::addCity(City)]+0x1c): undefined reference to `TourManager::destinationCities' 
/tmp/ccYnTr05.o: In function `TourManager::getCity(int)': 
tsp.cpp:(.text._ZN11TourManager7getCityEi[TourManager::getCity(int)]+0x14): undefined reference to `TourManager::destinationCities' 
/tmp/ccYnTr05.o: In function `TourManager::numberOfCities()': 
tsp.cpp:(.text._ZN11TourManager14numberOfCitiesEv[TourManager::numberOfCities()]+0x5): undefined reference to `TourManager::destinationCities' 
collect2: ld returned 1 exit status 

這裏是代碼片段：

class TourManager 
{ 
private: 

    static vector<City> destinationCities; 

public: 

    static void addCity(City city) 
    { 
     destinationCities.push_back(city); 
    } 

    static City getCity(int index) 
    { 
     return (City)destinationCities.at(index); 
    } 

    static int numberOfCities() 
    { 
     return (int)destinationCities.size(); 
    } 
}; 

我意識到矢量尚未初始化爲一個值，但不向量動態分配記憶？我不知道如何解決這個未定義的參考問題？是矢量還是別的問題？謝謝。

Answer 1

您只將向量聲明爲靜態數據成員，但您還需要在類之外定義它。例如

vector<City> TourManager::destinationCities;