“未定义参考”到模板类函数 [英] "undefined reference" to a template class function

问题描述

我正在为一个对象数组编写一个模板类，称为arrayobjclass，它保存了指向其他对象的指针，特别是我的实现中的其他数组。数组也实现为对象，称为arrayclass。
当我尝试使用以下行测试我的类时，查找可以进行最小更改的编译

I am writing a template class for an array of objects, call it arrayobjclass, which holds pointers to other objects, specifically to other arrays in my implementation. The arrays are implemented as objects as well, call them arrayclass. Looking for compilation ready with minimal changes.

。

g++ main.cpp arrayclass.cpp arrayobjclass.cpp -o arrayobj

我得到以下错误：

/tmp/ccEpROXj.o(.text+0x17c): In function `main':
: undefined reference to `arrayobjclass<arrayclass, int>::arrayobjclass(int)'
/tmp/ccEpROXj.o(.text+0x1dc): In function `main':
: undefined reference to `arrayobjclass<arrayclass, int>::addelem(arrayclass*)'
collect2: ld returned 1 exit status

我真的不明白什么是错的。任何帮助将不胜感激。代码的短相关部分如下，如果它有帮助。 THANKS IN ADVANCE！

I really can't understand what is wrong. any help would be appreciated. the short relevant part of the code is below if it helps. THANKS IN ADVANCE!

#include "arrayclass.h"
#include "arrayobjclass.h"
#include <iostream>

// 5 arrays of 10 maxsize each
#define MAXSIZE_array 10
#define NUMB_objs 5

using namespace std;

int main () {

    //create a simple array as an arrayclass object
    arrayclass * numbers1 = new arrayclass (MAXSIZE_array);

    //array of objects to hold pointers to simple arrays as created above
    arrayobjclass<arrayclass,int> * myobjs = new arrayobjclass<arrayclass,int> (NUMB_objs);

    //fill up the simple array
    int i;
    for (i=0; i<10; i++) {
        numbers1->addelem(i); 
    }

    //add a pointer to the simple array in my array of objects
    myobjs->addelem(numbers1);    
}

---

---

//arrayobjclass.h
//declarations of an array of pointers to objects

template <class obj, class key>
class arrayobjclass {

private:
    //obj * arrayptr;
    obj * objarray [];
    int maxsize;
    int totalelem;
public:
    arrayobjclass(int);
    bool addelem(obj *);
};

---

---

//arrayobjclass.cpp
//implementation of arrayobjclass, array of pointers to objects

#include "arrayobjclass.h"
#include "arrayclass.h"

template <class obj,class key>
arrayobjclass<obj,key>::arrayobjclass (int size){    
    maxsize=size;
    objarray = new obj[maxsize];
    totalelem = 0;
}

template <class obj, class key>
bool arrayobjclass<obj,key>::addelem (obj * newobj) {   
    if (totalelem < maxsize ) {
        objarray[totalelem] = newobj;
        totalelem ++;
        return true;
    }
    return false;
}

---

---

//arrayclass.h

class arrayclass {

private:
    int * arrayptr;
    int maxsize;
    int totalelem;
public:
    arrayclass(int);
    bool addelem(int);
};

---

---

//arrayclass.cpp

#include "arrayclass.h"

arrayclass::arrayclass (int size){   
    maxsize=size;
    arrayptr = new int[maxsize];
    totalelem = 0;
}

bool arrayclass::addelem (int addval) {    
    if (totalelem < maxsize ) {
        arrayptr[totalelem] = addval;
        totalelem ++;
        return true;
    }
    return false;
}

推荐答案

.cpp文件中的声明。模板声明和实现需要在同一翻译单元中可见。将模板实现放入您直接包含的标头中。

You can't put template declarations in .cpp files like that. Template declarations and implementation need to be visible in the same translation unit. Put template implementations in headers that you #include directly.

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