如何声明模板类的析构函数

Question

I get error while trying to compile following class

Stack.cpp:28: error: expected constructor, destructor, or type conversion before '::' token

#include <iostream>
using namespace std;

template <class T>
class Stack
{
public:
    Stack(): head(NULL) {};
    ~Stack();

    void push(T *);
    T* pop();

protected:
    class Element {
    public:
            Element(Element * next_, T * data_):next(next_), data(data_) {}
            Element * getNext() const { return next; }
            T * value() const {return data;}
    private:
            Element * next;
            T * data;
    };

    Element * head;
};

Stack::~Stack()
{
    while(head)
    {
            Element * next = head->getNext();
            delete head;
            head = next;
      }
 }

Answer 1

You are declaring a template class. You can either:

• implement the destructor within the class declaration, like this

   public: Stack(): head(NULL) {}; ~Stack() { // ... } 

• define the templated destructor outside the class declaration, like this

   template <class T> Stack<T>::~Stack() { // ... } 

However, if you attempt to define just Stack::~Stack() then the compiler does not know which type T you are implementing the destructor for.

Answer 2

template<typename T>
Stack<T>::~Stack()
{
    //...
}

This is generally valid for every method you define outside of the class' declaration, not just the destructor.

Answer 3

 Stack::~Stack()

should be

template <typename T>
Stack<T>::~Stack()

Answer 4

If you put the function after the class definition, you must specify the template aspect again as in:

template <class T>
Stack<T>::~Stack()
{
    ...
}

You don't need to do that if you define the function inside the class (but that constitutes a compiler hint to inline the function which you may or may not care about).

Answer 5

不确定，但也许这样......

template <class T>

Stack<T>::~Stack()