C++单例模式_实现与存储器managenet

Question

低于我代码不为comiling单例模式

（错误LNK2019：解析外部符号 “私人：__thiscall辛格尔顿::辛格尔顿（无效）”（?? 0Singleton @@ AAE @ XZ）在函数“public：static class Singleton * __cdecl Singleton :: returnOneInstance（void）”（？returnOneInstance @ Singleton @@ SAPAV1 @ XZ）中引用）

任何人都可以帮忙吗？我也想知道如何管理内存？谢谢

#include <iostream> 
#include <string> 
#include <vector> 
#include <algorithm> 
#include <iterator> 

using namespace std; 

class Singleton 
{ 
private: 
    Singleton(); 
    Singleton(const Singleton& sing); 
    void operator=(const Singleton& sing); 
    static Singleton* singleton; 
    /*The 'instance' field holds the reference of the one and only instance. 
     It is stored in a static variable because its scope has to be the class itself and not a particular instance. 
    */ 
public: 
    static Singleton* returnOneInstance(); 
    void printme() const; 
}; 

Singleton* Singleton::singleton=NULL; 
Singleton* Singleton::returnOneInstance(){ 
    if (!singleton){ 
     singleton=new Singleton; 
    } 
    return singleton; 
}; 

void Singleton::printme()const { 
    cout << "I'm the Singleton" << endl; 
} 

int main() 

{ 
    Singleton* m=Singleton::returnOneInstance(); 
    m->printme(); 

    system("PAUSE"); 
    return 0; 
} 

Answer 1

基本上ctr尚未定义。我通过添加{}空主体来解决这个问题。在这种情况下，你只有一次对象实例，所以除非你想释放单例的内存，否则没有内存管理。在这种情况下，您可以提供销毁该类并删除保留的内存。

以下是你的代码固定：

#include <iostream> 
#include <string> 
#include <vector> 
#include <algorithm> 
#include <iterator> 

using namespace std; 

class Singleton 
{ 
private: 
    Singleton(){}; 
    Singleton(const Singleton& sing); 
    void operator=(const Singleton& sing); 
    static Singleton* singleton; 
    /*The 'instance' field holds the reference of the one and only instance. 
    It is stored in a static variable because its scope has to be the class itself and not a particular instance. 
    */ 
public: 
    static Singleton* returnOneInstance(); 
    void printme() const; 

}; 

Singleton* Singleton::singleton=NULL; 

Singleton* Singleton::returnOneInstance() 
{ 
    if (!singleton){ 
     singleton=new Singleton; 
    } 
    return singleton; 
}; 

void Singleton::printme()const { 
    cout << "I'm the Singleton" << endl; 
} 

int main() 

{ 
    Singleton* m=Singleton::returnOneInstance(); 
    m->printme(); 

    system("PAUSE"); 
    return 0; 
}