不完整的类型

Question

我为'next'和'previous'变量得到了一个不完整的类型错误.我不确定我做错了什么,因为我在用C++编写类时非常生疏.任何帮助,将不胜感激!谢谢.

#include<iostream>

using namespace std;

class LinearNode
{
    public:
        //Constructor for the LinearNode class that takes no arguments 
        LinearNode();
        //Constructor for the LinearNode class that takes the element as an argument
        LinearNode(int el);
        //returns the next node in the set.
        LinearNode getNext();
        //returns the previous node in the set
        LinearNode getPrevious();
        //sets the next element in the set
        void setNext(LinearNode node);
        //sets the previous element in the set
        void setPrevious(LinearNode node);
        //sets the element of the node
        void setElement(int el);
        //gets the element of the node
        int getElement();

    private: 
        LinearNode next;
        LinearNode previous;
        int element;        
};//ends the LinearNode class

实施文件:

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

using namespace std;

//Constructor for LinearNode, sets next and element to initialized states
LinearNode::LinearNode()
{
    next = NULL;
    element = 0;
}//ends LinearNode default constructor

//Constructor for LinearNode takes an element as argument.
LinearNode::LinearNode(int el)
{
    next = NULL;
    previous = NULL;
    element = 0;
}//ends LinearNode constructor

//returns the next element in the structure
LinearNode::getNext()
{
    return next;
}//ends getNext function

//returns previous element in structure
LinearNode::getPrevious()
{
    return previous;
}//ends getPrevious function

//sets the next variable for the node
LinearNode::setNext(LinearNode node)
{
    next = node
}//ends the setNext function

//sets previous for the node
LinearNode::setPrevious(LinearNode node)
{
    previous = node;
}//ends the setPrevious function

//returns element of the node
LinearNode::getElement()
{
    return element;
}//ends the getelement function

//sets the element of the node
LinearNode::setElement(int el)
{
    element = el;
}//ends the setElement function

测试文件:

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

using namespace std;

int main()
{
    LinearNode node1, node2, move;
    node1.setElement(1);
    node2.setElement(2);

    node2.setNext(node1);
    node1.setPrevious(node2);

    move = node2;

    while(move.getNext() != NULL)
        cout << move.getElement() << endl;

}

Answer 1

您的类型具有递归定义,这是禁止的.

class LinearNode
{
private: 
    LinearNode next;
    LinearNode previous;
};

数据成员next和previous是的情况下(未引用或指针)LinearNode类,它尚未完全定义.

你可能想要这个:

class LinearNode
{
private: 
    LinearNode * next;
    LinearNode * previous;
};

Answer 2

您需要指定所有 .cpp 函数的返回类型。前任：

    //returns previous element in structure
LinearNode LinearNode::getPrevious()
{
    return previous;
}//ends getPrevious function