我的链接列表打印功能进入无限循环

Question

>linkedlist.h

#ifndef LINKEDLIST_H_
#define LINKEDLIST_H_
#include <iostream>
template <typename T>
class list{
public:
    list();
    class node;
    typedef T           value_type;
    typedef T&          reference;
    typedef node        node_type;
    typedef node_type*  node_pointer;
    list&           push_back(value_type);
    value_type      pop_front();
    node_pointer    begin() const;
private:
    node_pointer    head, tail;
};

template <typename T>
class list<T>::node{
public:
    node(value_type value = 0);
    void            setData(value_type);
    value_type      getData() const;
    void            setNext(node_pointer);
    node_pointer    getNext() const;
private:
    value_type      data;
    node_pointer    ptr_next;
};
template <typename T>
inline list<T>::node::node(value_type value) : data(value), ptr_next(nullptr){
}
template <typename T>
void list<T>::node::setData(value_type value){
    this->data = value;
}
template <typename T>
typename list<T>::value_type        list<T>::node::getData() const{
    return this->data;
}
template <typename T>
void list<T>::node::setNext(node_pointer ptr){
    this->ptr_next = ptr;
}
template <typename T>
typename list<T>::node_pointer  list<T>::node::getNext() const{
    return this->ptr_next;
}
template <typename T>
list<T>::list() : head(nullptr), tail(nullptr){
}
template <typename T>
list<T>&    list<T>::push_back(value_type value){
    node_pointer item = new node_type(value);
    if(this->tail) this->tail->setNext(item);
    this->tail = item;
    if(!this->head) this->head = this->tail;
    return *this;
}
template <typename T>
typename list<T>::value_type    list<T>::pop_front(){
    if(this->head){
        node_pointer    item = this->head;
        value_type      value = this->head->getData();
        this->head = this->head->getNext();
        delete item;
        return value;
    }
return 0;
}
template <typename T>
typename list<T>::node_pointer list<T>::begin() const{
    return this->head;
}
template <typename T>
std::ostream & operator<<(std::ostream &stream, list<T> &obj){
    typename list<T>::node_pointer ptr = obj.begin();
    while(ptr->getNext() != nullptr){
        stream << ptr->getData() << " ";
        ptr->setNext(ptr->getNext());
    }
    return stream;
}
#endif /* LINKEDLIST_H_ */

主.cpp

#include <iostream>
#include "LinkedList.h"
using std::cout;
using std::endl;
int main (int argc, char ** argv){ 
    list<int> mylist;
    mylist.push_back(5).push_back(1);
    cout << mylist;

    return 0;
}

我只是想创建一个重载operator<<的打印函数。 无论我做什么，我都找不到解决方案。这个重载运算符<<函数有什么问题？如果程序抛出错误，我该如何清理垃圾。析构函数应该如何？

Answer 1

template <typename T>
std::ostream & operator<<(std::ostream &stream, list<T> &obj){
    typename list<T>::node_pointer ptr = obj.begin();
    while(ptr != nullptr){
        stream << ptr->getData() << " ";
        ptr = ptr->getNext();
    }
    return stream;
}

我意识到我在打印功能中犯了一个逻辑错误。但我仍然想知道如何收集垃圾？