艺术家：：艺术家和艺术品：：艺术品

Question

我对这个多文件类很陌生，我对我的两个类都有一个未定义的引用，我认为它与我的初始化和默认构造函数有关，但老实说，我一点也不知道这是否是正确的。任何帮助都是非常感谢的。

main.cpp

#include "Artist.h"
#include "Artwork.h"
#include <iostream>
#include <string>
using namespace std;

int main() {
   string userTitle, userArtistName;
   int yearCreated, userBirthYear, userDeathYear;

   getline(cin, userArtistName);
   cin >> userBirthYear;
   cin.ignore();
   cin >> userDeathYear;
   cin.ignore();
   getline(cin, userTitle);
   cin >> yearCreated;
   cin.ignore();

   Artist userArtist =  Artist(userArtistName, userBirthYear, userDeathYear);

   Artwork newArtwork = Artwork(userTitle, yearCreated, userArtist);

   newArtwork.PrintInfo();
}

Artist.h

#ifndef ARTISTH
#define ARTISTH

#include <string>
using namespace std;

class Artist{
   public:
      Artist();

      Artist(string artistName, int birthYear, int deathYear);

      string GetName() const;

      int GetBirthYear() const;

      int GetDeathYear() const;

      void PrintInfo() const;

   private:
      string artistName;
      int birthYear;
      int deathYear;

};

#endif

Artist.cpp

#include "Artist.h"
#include <iostream>
#include <string>
using namespace std;

Artist::Artist()
{
   artistName = "unknown";
   birthYear = -1;
   deathYear = -1;
}



string Artist::GetName() const 
{
   return artistName;   
}

int Artist::GetBirthYear() const
{
   return birthYear;   
}

int Artist::GetDeathYear() const
{
   return deathYear;
}

void Artist::PrintInfo() const
{
   if(deathYear > 0 && birthYear > 0)
   {
   cout << "Artist: " << artistName <<" ("<< birthYear << " to "<< deathYear << ")" << 
endl;   
   }
   else if(birthYear > 0 && deathYear < 0)
   {
   cout << "Artist: " << artistName <<" ("<< birthYear << " to present)" << endl;  
   }
   else if(birthYear<0 && deathYear<0)
   {
   cout << "Artist: " << artistName << " (unknown)" << endl;  
   }
}

Artwork.h

#ifndef ARTWORKH
#define ARTWORKH

#include "Artist.h"

class Artwork{
   public:
      Artwork();

      Artwork(string title, int yearCreated, Artist artist);

      string GetTitle();

      int GetYearCreated();

      void PrintInfo();

   private:
      string title;
      int yearCreated;
  
      Artist artist;

};

#endif

Artwork.cpp

#include "Artwork.h"
#include <iostream>

Artwork::Artwork()
{
   cout <<"Artwork has started." << endl;
   title = "unknown";
   yearCreated = -1;
   Artist artist(); //here im not sure how to initialize an object inside of an object
}


string Artwork::GetTitle()
{
   return title;   
}

int Artwork::GetYearCreated()
{
   return yearCreated;   
}

void Artwork::PrintInfo()
{
   artist.PrintInfo();
   cout << "Title: " << title << ", " << yearCreated << endl;

}

Answer 1

我是正确的，我需要初始化一个默认的(没有输入参数)构造函数和一个带有输入参数的构造函数。

若要正确编写默认和参数构造函数，请执行以下操作

Artwork::Artwork(string n, int y, Artist a)
{
   title = n;
   yearCreated = y;
   artist = a;
}//constructor with given input

Artwork::Artwork()
{
   title = "unknown";
   yearCreated = -1;
}//if input is not given for any fields, refer to this constructor

注意，默认构造函数没有对象，老实说，我不确定是否有方法初始化空白对象，如果有，为什么没有必要。

艺术家构造函数看起来是一样的，

Artist::Artist(string name, int birth, int death)
{
   artistName = name;
   birthYear = birth;
   deathYear = death;
}

Artist::Artist()
{
   artistName = "unknown";
   birthYear = -1;
   deathYear = -1;
}