Question

下面我的代码没有针对单例模式进行编译

（错误LNK2019：未解析的外部符号＆＃34;私人：__thiscall Singleton :: Singleton（无效）＆＃34;（?? 0Singleton @@ AAE @ XZ）在函数＆＃34; public：static class Singleton中引用* __cdecl Singleton :: returnOneInstance（void）＆＃34;（？returnOneInstance @ Singleton @@ SAPAV1 @ XZ））

任何人都可以帮忙吗？我也想知道如何管理记忆？感谢

#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{}空体来修复此问题。在这种情况下，你只有一次对象的实例，所以没有内存管理，除非你想释放单例的内存。在这种情况下，您可以提供销毁类并删除保留的内存。

以下是您修改的代码：

    #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;
}

C ++单例模式_实现和内存管理网

1 个答案: