如何在main（）中调用构造函数？

Question

我正在为我的构造函数使用a string和intas作为变量的程序friend。我有我的大多数项目的完成，但由于我是新来这个话题的friendS和构造与C ++，我不知道如何实现我的电话main()使用这些参数，并开始对我的工作istream，并ostream询问用户输入值并开始打印。

有人可以指导我正确的方法吗？

这些是我当前的构造函数：

jellyBeanFlavors::jellyBeanFlavors()
{
    flavor = "null";
    jellyBeans = 0;
}

jellyBeanFlavors::jellyBeanFlavors(int newJellyBeans)
{
    flavor = "null";
    jellyBeans = newJellyBeans;
}

jellyBeanFlavors::jellyBeanFlavors(string newFlavor, int newjellyBeans)
{
    flavor = newFlavor;
    jellyBeans = newjellyBeans;
}

void jellyBeanFlavors::output()
{
    cout << flavor << " " << jellyBeans << endl;
}

现在，我尝试在此处实现我的对象，并开始提出要输入的问题，然后使用istream函数进行打印：

int main ()

    {
        jellyBeanFlavors::jellyBeanFlavors(string newFlavor, int newjellyBeans);

        jellyBeanFlavors();
        jellyBeanFlavors myFirstFlavor = jellyBeanFlavors.the;
        jellyBeanFlavors mySecondFlavor;
        jellyBeanFlavors total = 0;

        cout << "Your first flavor  is: "<< myFirstFlavor. << endl;
        cin >> myFirstFlavor;
        cout << "Your second flavor is: "<< mySecondFlavor << endl;
        cin >> mySecondFlavor;
        cout << "The expected result of adding" << " the first flavor loaded with" << mySecondFlavor <<" in the quantity with jellybean2 loaded with 6 in the quantity is: ";
        cout << "a jellybean with a quantity of 11.
        cout << "the result of adding jellybean1 and jellybean two is: " << jellybean1 + jellybean2 << endl;


        // this isnt implemented right but i need advice please on how to call my objects from my main class.


        system("pause");

        return 0;
    }

这样您就不会感到困惑，这是我的主要课程：

    #include <iostream>
    #include <string>
    using namespace std;

    class jellyBeanFlavors
    {
        friend jellyBeanFlavors operator + (jellyBeanFlavors theFirstJellyBean, jellyBeanFlavors theSecondJellyBean);//sums
        friend jellyBeanFlavors operator - (jellyBeanFlavors theFirstJellyBean, jellyBeanFlavors theSecondJellyBean);//(binary) substracts
        friend jellyBeanFlavors operator - (jellyBeanFlavors theFirstJellyBean);// (unary) checks negatives
        friend jellyBeanFlavors operator * (jellyBeanFlavors theFirstJellyBean,jellyBeanFlavors theSecondJellyBean);//multiplies
        friend jellyBeanFlavors operator / (jellyBeanFlavors theFirstJellyBean,jellyBeanFlavors theSecondJellyBean);//divides
        friend jellyBeanFlavors operator == (jellyBeanFlavors theFirstJellyBean,jellyBeanFlavors theSecondJellyBean);//compares
        friend jellyBeanFlavors operator < (jellyBeanFlavors theFirstJellyBean,jellyBeanFlavors theSecondJellyBean);// less than
        friend jellyBeanFlavors operator > (jellyBeanFlavors theFirstJellyBean,jellyBeanFlavors theSecondJellyBean);//greater than
        friend ostream& operator << (ostream& outputStream, const jellyBeanFlavors& jellyBeanOutput);// output
        friend istream& operator >> (istream& inputStream, jellyBeanFlavors& jellyBeanInput);//input 

    public:
        jellyBeanFlavors();
        jellyBeanFlavors(int);
        jellyBeanFlavors(string, int);
        void output();

    private:
        string flavor;
        int jellyBeans;

    };

>通过添加对象并重载它们来解决程序：

我的程序解决方案，方法是添加对象并重载它们：

 int main ()
    {   
        system("cls");
        char op;
        jellyBeanFlavors obj1,obj2,obj3;
        do{
            cin>>obj1;  //flavor
            cin>>obj2;  //amount 

            system("cls");
            cout<<"JELLYBEANS:"<<endl;

            obj3=obj1+obj2;
            cout<<"\n The Sum is : ";
            obj3.output();

            obj3=obj1-obj2;
            cout<<"\n The Substraction is : ";
            obj3.output();

            obj3=obj1*obj2;
            cout<<"\n The Multiplication is: ";
            obj3.output();

            obj3=obj1/obj2;
            cout<<"\n The Divide operation is : ";
            obj3.output();

            cout<<"\n"; 
            obj3 = obj1==obj2;
            obj3.output();
            cout<<"\n";

            obj3 = obj1>obj2;
            obj3.output();
            cout<<"\n";

            obj3 = obj1<obj2;
            obj3.output();
            cout<<"\n";

            obj3 = -obj1;
            obj3.output();
            cout<<"\n";

            obj3 = -obj2;
            obj3.output();
            cout<<"\n";

            cout<<"\n\nPress A/a and Enter to continue or 0 to exit"<<endl;
            cin>>op;
            if(op = 0)
            {
                exit(0);
            }
        }while(op =='a'|| op=='A');


        system("pause");
    }

Answer 1

除了您提供的代码中的许多其他语法错误之外，构造具有自动存储持续时间的对象应如下所示：

class A {
public:
    A() { }          // <-- default constructor
    A(int i) { }     // <-- constructor taking int

    void foo() { }   // <-- member function ("method")
    static s() { }   // <-- static function
};

在某处：

A a;           // <-- constructs object using the default constructor
A a2 = A();    // <-- equivalent to the previous one (copy initialization)
A a3(a2);      // <-- copy constructor ~ constructs a3 using the a2 object
A a4(7);       // <-- constructs object using the constructor taking int

// now when you have some objects, you can call member functions
// (i.e. invoke the behavior they provide)
a.foo();

// static functions are not dependent on objects:
A::s();        // <-- calls static function defined within namespace of class A

在继续编写更多代码之前，请考虑花一些时间阅读一些体面的书。
如果您不确定要读什么书，可以在这里找到一本：《权威C ++书籍指南和清单》