c ++模板化类没有链接

Question

template<typename AT>
class growVector {

        int size;
        AT **arr;
        AT* defaultVal;

    public:

        growVector(int size , AT* defaultVal);   //Expects number of elements (5) and default value (NULL)
        AT*& operator[](unsigned pos);
        int length();
        void reset(int pos);    //Resets an element to default value
        void reset();           //Resets all elements to default value
        ~growVector();
};

和.cpp是

template<typename AT>
growVector<AT>::growVector(int size, AT* defaultVal) {
    arr = new AT*[size];
    this->size = size;
    for (int i = 0 ; i < size; i++){
        arr[i] = defaultVal;
    }
}

template<typename AT>
AT*& growVector<AT>::operator [](unsigned pos){
    if (pos >= size){
        int newSize = size*2;
        AT** newArr = new AT*[newSize];
        memcpy(newArr, arr, sizeof(AT)*size);
        for (int i = size; i<newSize; i++)
            newArr[i] = defaultVal;
        size = newSize;
        delete arr;
        arr = newArr;
    }
    return arr[pos];
}

//template<typename AT>
//const AT*& growVector<AT>::operator [](unsigned pos) const{
//  if (pos >= size)
//      throw std::range_error("index out of range in constant vector");
//  }
//  return NULL;
//}
template<typename AT>
int growVector<AT>::length(){
    return size;
}

template<typename AT>
growVector<AT>::~growVector(){
    delete arr;
}

template<typename AT>
void growVector<AT>::reset(int pos){
    if (pos>=size)
        throw new std::range_error("index out of bounds");
    arr[pos] = defaultVal;
}

template<typename AT>
void growVector<AT>::reset(){
    for (int pos = 0; pos<size; pos++)
        arr[pos] = defaultVal;
}

......非常基本的

我用它

int main() {

    growVector<char> gv(5, (char*)NULL);
    char* x = NULL;
    for (int i = 0; i< 50; i++){
        gv[i] = x;
    }
    gv.reset();
    return 0;
}

它编译但链接器说:

Invoking: GCC C++ Linker
g++ -pthread -o"base"  ./src/base.o  ./src/base/baseController.o ./src/base/baseThreads.o ./src/base/utils.o  ./src/base/utils/utilClasses.o   
./src/base.o: In function `main':
/home/dario/workspace/base/Debug/../src/base.cpp:95: undefined reference to `baseUtils::growVector<char>::growVector(int, char*)'
/home/dario/workspace/base/Debug/../src/base.cpp:98: undefined reference to `baseUtils::growVector<char>::operator[](unsigned int)'
/home/dario/workspace/base/Debug/../src/base.cpp:100: undefined reference to `baseUtils::growVector<char>::reset()'
/home/dario/workspace/base/Debug/../src/base.cpp:101: undefined reference to `baseUtils::growVector<char>::~growVector()'
/home/dario/workspace/base/Debug/../src/base.cpp:101: undefined reference to `baseUtils::growVector<char>::~growVector()'
collect2: ld returned 1 exit status

我真的很无能为力

Answer 1

对于模板,通常,定义应放在头文件中,因为所有编译单元都需要它.

当您知道将调用模板类的类型时,有一些技巧可以避免这样做,但对于真正的通用问题,它只是不起作用.

注意:

如果我是你,我会使用一个STL容器,结果不太可能是马车.