读取对象数组时编译时出错

Question

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

class Film {
private:
    string name;
    int year_prod;
    string producer;
    string main_actor;

public:
    Film();
    void print()
    {
        cout << "\nThe name of movie: " << name;
        cout << "\nThe year of produced: " << year_prod;
        cout << "\nProducer: " << producer;
        cout << "\nMain actor: " << main_actor << endl;
    }
    void SetName(string xName)
    {
       name = xName;
    }

    string GetName()
    {
       return name;
    }

    void SetYearP(int xYearP)
    {
        year_prod = xYearP;
    }

    int GetYearP()
    {
        return year_prod;
    }

    void SetProducer(string xProducer)
    {
        producer = xProducer;
    }

    string GetProducer()
    {
        return producer;
    }

    void SetMaina(string xMaina)
    {
        main_actor = xMaina;
    }

    string GetMaina()
    {
        return main_actor;
    }


};


int main()
{
    Film obs[100]; // maximum of 100 hundred films
    int n;
    cout << "how many films ";
    cin >> n;
    for (int i = 0; i < n; ++i)
    {
        string name;
        int year;
        string prod;
        string actor;
        cout << "enter the film name ";
        cin >> name;
        cout << "enter the production year ";
        cin >> year;
        cout << "enter the producer name ";
        cin >> prod;
        cout << "enter the actor name ";
        cin >> actor;
        obs[i].SetName(name);
        obs[i].SetYearP(year);
        obs[i].SetProducer(prod);
        obs[i].SetMaina(actor);
    }
} 

我已经完成了一半的代码，但在编译时出现错误提示：函数 _main AND 1 中引用的未解析的外部符号“public: __thiscall Film::Film(void)”(??0Film@@QAE@XZ)未解决的外部。我不确定我是否以正确的方式从用户输入中获得了 n Film 的对象，因为我仍然是 OOP 的初学者。

Answer 1

你没有实现你的构造函数：

public:
    Film();//<-- declared, but not defined.

如果你不希望你的构造函数做任何事情，只需添加一个空的主体：

public:
    Film() {};

或者更好的是，明确地将其声明为默认构造函数：

public:
    Film()=default;

Answer 2

请试试这个。希望这会有所帮助。

class Film {
...
...
...
public:
        //Film(); Remove this line if you are not defining Film()
        void print()
        {
            cout << "\nThe name of movie: " << name;
            cout << "\nThe year of produced: " << year_prod;
            cout << "\nProducer: " << producer;
            cout << "\nMain actor: " << main_actor << endl;
        }
...
...
...
}

如果您希望它成为默认构造函数，请添加一个空块 Film(){}

Answer 3

你必须为你的类实现构造函数。构造函数是创建类实例的方法。 set函数的目的是修改对象的属性，但属性的初始化必须在构造函数中完成。

例如：

public:
  //default constructor: it does not take 
  //anything as input, it sets name as an 
  //empty string and the year to 1900
  Film(){
    name = "";
    year = 1900;
  }
  // It creates a Film object, whose name 
  // is NAME and whose year is YEAR
  Film(string NAME, int YEAR){
    name = NAME;
    year = YEAR;
  }

// set function which allows to modify the 
// year of a Film object.
void setYear(int newYear){
  year = newYear;
}

查看here 了解快速介绍。

编辑：您可能希望将默认构造函数设置为

Film(){};

这样你必须调用所有的集合函数来初始化它的属性。