c ++类继承，未定义引用'Class :: Constructor（）' [英] c++ class inheritance, undefined reference to 'Class::Constructor()'
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问题描述
编辑：已发布固定代码在底部。感谢大家的帮助！
我只是学习c + +，我有继承的麻烦。我搜索和搜索，尝试了任何我可以，但我不能得到这个代码编译，同时保留我想要的功能。
我觉得我犯了一个愚蠢的错误，或者我只是错过了一个大的概念，但如果任何人都可以看看它，我真的很感激它！
如果我注释掉StarSystem构造函数中创建对象的3行，那么它会编译，所以我知道这与该问题有关。
#include< iostream>
#include< vector>
#include< string>
#include< stdlib.h>
#include< time.h>
using namespace std;
class SystemBody
{
public：
SystemBody（）;
int systembodyindex;
int starsystemindex;
SystemBody（int systembodyindex，int starsystemindex）
{
cout< StarSystem< starsystemindex< ：创建空SystemBody< systembodyindex< endl
}
};
class Star：public SystemBody
{
public：
Star（）;
string startype;
Star（int systembodyindex，int starsystemindex）
{
cout< StarSystem<< starsystemindex< ：将空SystemBody转换为星< systembodyindex< endl
}
};
class Planet：public SystemBody
{
public：
Planet（）;
string planettype;
Planet（int systembodyindex，int starsystemindex）
{
cout< StarSystem<< starsystemindex< ：将空SystemBody转换为Planet< systembodyindex< endl
}
};
class ExitNode：public SystemBody
{
public：
ExitNode（）;
vector< int>连接索引
ExitNode（int systembodyindex，int starsystemindex）
{
cout< StarSystem<< starsystemindex< ：将空SystemBody转换成退出节点< systembodyindex< endl
}
};
class StarSystem
{
public：
StarSystem（）;
int starsystemindex;
vector< StarSystem>连接列表
vector< Planet> planetlist是什么意思
StarSystem（int index）
{
starsystemindex = index;
cout< - 创建StarSystem：< starsystemindex< endl
int numberofbodies =（rand（）％4）+ 2;
for（int i = 0; i< numberofbodies; i + = 1）
{
if（i == 0）
{
星体，starsystemindex）;
}
else if（i == numberofbodies）
{
ExitNode body（i，starsystemindex）;
}
else
{
星球体（i，starsystemindex）;
}
}
}
void addConnection（StarSystem connectedstarsystem）
{
cout< ; --StarSystem< starsystemindex< ：添加到StarSystem的连接< connectedstarsystem.starsystemindex< endl
connectedlist.push_back（connectedstarsystem）;
}
};
int main（）
{
srand（time（0））;
StarSystem starsystem0（0）;
return 0;
}
编辑：
感谢大家的帮助！只是在这里张贴固定代码，以防任何未来可能发现这是有用的。
#include< iostream>
#include< vector>
#include< string>
#include< stdlib.h>
#include< time.h>
using namespace std;
class SystemBody
{
public：
int systembodyindex;
int starsystemindex;
SystemBody（）
{
cout<< ----系统体无创建参数< endl
}
SystemBody（int bodyindex，int systemindex）
{
systembodyindex = bodyindex;
starsystemindex = systemindex;
cout<< ----星系统< starsystemindex< ：创建空SystemBody< systembodyindex< endl
}
};
class Star：public SystemBody
{
public：
Star（int bodyindex，int systemindex）：SystemBody（bodyindex，systemindex）
{
cout<< ----星系统< starsystemindex< ：将空SystemBody转换为星< systembodyindex< endl
}
};
class Planet：public SystemBody
{
public：
Planet（int bodyindex，int systemindex）：SystemBody（bodyindex，systemindex）
{
cout<< ----星系统< starsystemindex< ：将空SystemBody转换为Planet< systembodyindex< endl
}
};
class ExitNode：public SystemBody
{
public：
ExitNode（int bodyindex，int systemindex）：SystemBody（bodyindex，systemindex）
{
cout<< ----星系统< starsystemindex< ：将空SystemBody转换成ExitNode< systembodyindex< endl
}
};
class StarSystem
{
public：
int starsystemindex;
vector< StarSystem>连接表
vector< Planet> planetlist是什么意思
StarSystem（int index）
{
starsystemindex = index;
cout<< - 创建StarSystem：< starsystemindex< endl
int numberofbodies =（rand（）％4）+ 2;
for（int i = 0; i <= numberofbodies; i + = 1）
{
if（i == 0）
{
星体i，starsystemindex）;
}
else if（i == numberofbodies）
{
ExitNode body（i，starsystemindex）;
}
else
{
星球体（i，starsystemindex）;
}
}
}
};
int main（）
{
srand（time（0））;
StarSystem starsystem0（0）;
return 0;
}
解决方案
也许只是我，您的构造函数在这里是一个没有定义的简单的声明：
class StarSystem
{
public：
StarSystem（）; //< --- Undefined！
你有一个构造函数声明，但是没有定义这个构造函数的实际内容。 p>
如果它是一个什么都不做的构造函数，请执行
StarSystem {} //定义。
//内部没有发生，但是一切都得到默认构造！
注意，当发布这些类型的东西时，它有助于发布错误号，一个注释或某种指示错误发生的地方（所以我们可以看到它在你的巨大的blob代码）。
编辑：
请注意，如果你根本不使用该构造函数，只需删除它。
Edit: Posted fixed code at the bottom. Thanks everyone for your help!
I am just learning c++ and am having trouble with inheritance. I have searched and searched and tried anything I can but I can not get this code to compile while retaining the functionality that I want it to have.
I feel like I am making a stupid mistake or maybe I'm just missing some big concept, but if anyone could take a look at it I'd really appreciate it!
If I comment out the the 3 lines in the StarSystem Constructor that create objects, then it compiles, so I know this has to do with the issue.
#include <iostream>
#include <vector>
#include <string>
#include <stdlib.h>
#include <time.h>
using namespace std;
class SystemBody
{
public:
SystemBody();
int systembodyindex;
int starsystemindex;
SystemBody(int systembodyindex, int starsystemindex)
{
cout << "StarSystem " << starsystemindex << ": creating empty SystemBody " << systembodyindex << endl;
}
};
class Star : public SystemBody
{
public:
Star();
string startype;
Star(int systembodyindex, int starsystemindex)
{
cout << "StarSystem " << starsystemindex << ": converting empty SystemBody into Star " << systembodyindex << endl;
}
};
class Planet : public SystemBody
{
public:
Planet();
string planettype;
Planet(int systembodyindex, int starsystemindex)
{
cout << "StarSystem " << starsystemindex << ": converting empty SystemBody into Planet " << systembodyindex << endl;
}
};
class ExitNode : public SystemBody
{
public:
ExitNode();
vector<int> connectedindexlist;
ExitNode(int systembodyindex, int starsystemindex)
{
cout << "StarSystem " << starsystemindex << ": converting empty SystemBody into Exit Node " << systembodyindex << endl;
}
};
class StarSystem
{
public:
StarSystem();
int starsystemindex;
vector<StarSystem> connectedlist;
vector<Planet> planetlist;
StarSystem(int index)
{
starsystemindex = index;
cout << "--Creating StarSystem: " << starsystemindex << endl;
int numberofbodies = (rand() % 4) + 2;
for ( int i = 0; i < numberofbodies; i +=1 )
{
if ( i == 0 )
{
Star body(i, starsystemindex);
}
else if ( i == numberofbodies )
{
ExitNode body(i, starsystemindex);
}
else
{
Planet body(i, starsystemindex);
}
}
}
void addConnection(StarSystem connectedstarsystem)
{
cout << "--StarSystem " << starsystemindex << ": Adding connection to StarSystem " << connectedstarsystem.starsystemindex << endl;
connectedlist.push_back(connectedstarsystem);
}
};
int main()
{
srand(time(0));
StarSystem starsystem0(0);
return 0;
}
EDIT:
thanks to everyone for your help! just posting the fixed code here in case any one in the future might find this useful.
#include <iostream>
#include <vector>
#include <string>
#include <stdlib.h>
#include <time.h>
using namespace std;
class SystemBody
{
public:
int systembodyindex;
int starsystemindex;
SystemBody ( )
{
cout << "----SystemBody BEING CREATED WITH NO PARAMETERS" << endl;
}
SystemBody ( int bodyindex, int systemindex )
{
systembodyindex = bodyindex;
starsystemindex = systemindex;
cout << "----StarSystem " << starsystemindex << ": creating empty SystemBody " << systembodyindex << endl;
}
};
class Star : public SystemBody
{
public:
Star ( int bodyindex, int systemindex ) : SystemBody ( bodyindex, systemindex )
{
cout << "----StarSystem " << starsystemindex << ": converting empty SystemBody into Star " << systembodyindex << endl;
}
};
class Planet : public SystemBody
{
public:
Planet ( int bodyindex, int systemindex ) : SystemBody ( bodyindex, systemindex )
{
cout << "----StarSystem " << starsystemindex << ": converting empty SystemBody into Planet " << systembodyindex << endl;
}
};
class ExitNode : public SystemBody
{
public:
ExitNode ( int bodyindex, int systemindex ) : SystemBody ( bodyindex, systemindex )
{
cout << "----StarSystem " << starsystemindex << ": converting empty SystemBody into ExitNode " << systembodyindex << endl;
}
};
class StarSystem
{
public:
int starsystemindex;
vector<StarSystem> connectedlist;
vector<Planet> planetlist;
StarSystem ( int index )
{
starsystemindex = index;
cout << "--Creating StarSystem: " << starsystemindex << endl;
int numberofbodies = (rand() % 4 ) + 2;
for ( int i = 0; i <= numberofbodies; i +=1 )
{
if ( i == 0)
{
Star body(i, starsystemindex);
}
else if ( i == numberofbodies )
{
ExitNode body(i, starsystemindex);
}
else
{
Planet body(i, starsystemindex);
}
}
}
};
int main()
{
srand(time(0));
StarSystem starsystem0(0);
return 0;
}
解决方案
Perhaps it's just me, but your Constructor here is a simple declration that's not been defined:
class StarSystem
{
public:
StarSystem(); // <--- Undefined!
You have a constructor declared, but there's no definition of what's actually going on in this constructor.
If it's a constructor that just does nothing, do
StarSystem () {} // Defined.
// Nothing happens inside, but everything gets default-constructed!
As a side note, when posting these kinds of things, it helps to post the error number and put a comment or some kind of indicator of where the error is happening (so we can see it in your giant blob of code).
EDIT: As an important note, if you're not using that constructor at all, just delete it.
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