c++ - 如何使用静态对象和方法!？ C++ 挫败感

Question

所以我已经花了几个小时来完成我认为会快速而简单的项目，但我无法让它工作!这让我很沮丧，哈哈，我必须接近，但也许我不是。

我将在我的代码中添加注释，解释它应该做什么。本质上它使用私有(private)构造函数和析构函数。一个成员整数，然后是一个公共(public)静态函数，用于返回对类中对象的引用 - 以及一个应该显示成员整数并递增它的公共(public)函数。我不断收到范围和初始化错误。

错误如下:

Singleton.h: In function ‘int main(int, char**)’:
Singleton.h:28:2: error: ‘Singleton::Singleton()’ is private
main.cpp:38:12: error: within this context
Singleton.h:29:2: error: ‘Singleton::~Singleton()’ is private
main.cpp:38:12: error: within this context

任何帮助或建议将不胜感激!

这是我的代码(Singleton.h、Singleton.cpp、main.cpp):

Singleton.h:

#ifndef SINGLETON_H
#define SINGLETON_H
#include <iostream>
#include <string>
#include <fstream>
#include <cstdlib>

class Singleton {

public:
    static Singleton& instance(); //returns a reference to a Singleton obj
    void sendOutput(); //prints member variable and increments it
private:
    int myInt; //member integer-variable
    Singleton(); //constructor
    ~Singleton(); //destructor

};
#endif

单例.cpp:

#include <string>
#include "Singleton.h"

using namespace std;

//Displays to console that the obj was created. Initializes the member variable
Singleton::Singleton(){
    myInt = 0; //member variable
    cout << "Singleton Object Created!" << endl;
}

//destructor - displays to console that the Singleton object was destructed
Singleton::~Singleton(){
   // delete myObj;
    cout << "Singleton Object Destructed!" << endl;
}

//display member variable value and increment
void Singleton::sendOutput(){
    cout << "Request to send data to output to console" << endl;
    cout << "Integer Value: " << myInt << endl;
    myInt++;
}

//REQUIRED: Static method with a reference to an object of this class return type
//create a static Singleton object and return it
Singleton& Singleton::instance(){
    static Singleton myObj;
    return myObj;
}

ma​​in.cpp:

#include "Singleton.h"
#include <string>
#include <iostream>
#include <cstdlib>

using namespace std;

//Another requirement - demo static variables
void static_test(){
    static int a = 1;
    cout << a << endl;
    a++;
}

int main(int argc, char * argv[]){

    static_test();
    static_test();
    static_test();


//messed around with this for awhile - got it to work a few times
//messed it up a few more times O.o 

    Singleton mySingletonObj;
    Singleton& sRef = Singleton::instance();
    //sRef = Singleton::instance();
    sRef.sendOutput();

    return 0;
}

---

想法/建议/问题/疑虑？ 任何事情都会有助于缓解这给我带来的挫败感，哈哈。给我带来这样的问题似乎太简单了。谢谢!

Answer 1

该范围内禁止:

Singleton mySingletonObj;

应该没问题:

Singleton& sRef = Singleton::instance();

引用文献不可重新分配:

sRef = Singleton::instance();

应该没问题:

sRef.sendOutput();

另外，删除它——该语言已经指定了对象的生命周期和存储，并负责销毁它:

delete myObj;

您还应该删除复制类型的功能:

Singleton(); //constructor
Singleton(const Singleton&) = delete; // deleted copy constructor