当我包含.h时程序没有编译，当我包含.cpp

Question

我有这三个文件，main.cpp，DynamicArray.cpp，DynamicArray.h。在两个cpp文件中我都包含DynamicArray.h，我收到以下错误。

$ g++ main.cpp DynamicArray.cpp 
/tmp/ccDGRYws.o: In function `testDynamicArray()':
main.cpp:(.text+0x11): undefined reference to `DynamicArray<int>::DynamicArray()'
main.cpp:(.text+0x1d): undefined reference to `DynamicArray<int>::DynamicArray()'
main.cpp:(.text+0x39): undefined reference to `DynamicArray<int>::~DynamicArray()'
main.cpp:(.text+0x5a): undefined reference to `DynamicArray<int>::add(int)'
main.cpp:(.text+0x72): undefined reference to `DynamicArray<int>::size()'
main.cpp:(.text+0xb8): undefined reference to `DynamicArray<int>::~DynamicArray()'
main.cpp:(.text+0xc9): undefined reference to `DynamicArray<int>::~DynamicArray()'
collect2: error: ld returned 1 exit status

当我将main.cpp中的DynamicArray.h更改为DynamicArray.cpp时，它可以正常工作。为什么不能使用.h？

的main.cpp

#include <iostream>
#include <assert.h>

#include "DynamicArray.h"

void testDynamicArray(){

    DynamicArray<int> array1;
    array1 = DynamicArray<int>();

    int initialSize = 10;  

    for (int i = 0; i < initialSize; i++) {
        array1.add(i);
    }

    assert(array1.size() == initialSize);

    std::cout << "All tests for DynamicArray pass." << std::endl;
}



int main(){
    testDynamicArray();
}

DynamicArray.cpp

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

template <typename T>
DynamicArray<T>::DynamicArray(){
    numElements = 0;
    arraySize = 10;
    theArray = new T[arraySize];
}

template <typename T>
DynamicArray<T>::~DynamicArray(){
    delete[] theArray;    
}

template <typename T>
int DynamicArray<T>::size(){
    return numElements;
}

template <typename T>
bool DynamicArray<T>::isEmpty(){
    return (numElements == 0);
}

template <typename T>
void DynamicArray<T>::increaseSize(){
        T* tempArray = new T[arraySize * 2];

        for(int i = 0; i <= numElements; i++) {
            tempArray[i] = theArray[i];
        }

        delete[] theArray;
        theArray = tempArray;

        arraySize *= 2;
}

template <typename T>
void DynamicArray<T>::insert(T newElement, int index){
    if (numElements == arraySize) {
        increaseSize();
    }

    for (int i = numElements; i >= index ; i--) {
        theArray[i] = theArray[i-1];
    }

    theArray[index] = newElement;
    numElements++;
}

template <typename T>
void DynamicArray<T>::add(T newElement){
    if(numElements == arraySize)
        increaseSize();

    theArray[numElements] = newElement;

    numElements++;
}

template <typename T>
T DynamicArray<T>::get(int index){
    return theArray[index];
}

template <typename T>
bool DynamicArray<T>::deleteIndex(int index){

    if(index < 0 || index >= numElements)
        return false;

    for (int i = index; i < numElements-1; i++) 
    {
        theArray[i] = theArray[i+1];
    }

    numElements--;

    return true;
}

DynamicArray.h

#ifndef DYNAMICARRAY
#define DYNAMICARRAY

template <typename T>
class DynamicArray{
    private:
    T* theArray;
    int numElements;
    int arraySize;
    void increaseSize();

    public:
    DynamicArray();
    ~DynamicArray();
    int size();
    bool isEmpty();
    void insert(T newElement, int index);
    void add(T newElement);
    bool deleteIndex(int index);
    T get(int index);
};

#endif