如何修复不完全类型错误c ++？ [英] How to fix incomplete type error c++?

问题描述

我想使用级别顺序遍历构建树。当我声明我的Queue对象在私有作用域，我得到错误字段'q'有不完全类型'队列'我的程序工作，如果我在addTreeNode（int integer）函数声明一个队列，但是当我移动它头文件，我得到新的错误从我已经读了似乎Tree类不知道多少内存分配给Queue对象如何解决这个？

I want to build a tree using level order traversal. When I declare my Queue object in the private scope, I get the error "field 'q' has incomplete type 'Queue'. My program works if I declare a Queue in the addTreeNode(int integer) function, but when I move it to the header file, I get the new error. From what I have read it seems that the Tree class does not know how much memory to allocate to the Queue object. How to I fix this?

编辑：对于浏览这个问题的任何人，这个问题与包含文件等无关。这里的问题是Tree有一个队列的实例，而Queue和Tree是朋友类，这意味着他们可以访问对我的问题的解决方案是让Queue成为一个模板类。

For anyone browsing this question, the problem has nothing to do with inclusions files etc. The problem here is that Tree has an instance of a Queue, while Queue and Tree are friend classes, meaning they have access to each other's data members. This forces a situation that is circular and wonks out c++. The solution to my problem was to make Queue a template class.

这里是主类：

#include <cstdlib>
#include "Tree.cpp"

using namespace std;

int main() {

    Tree tree;
    tree.addTreeNode(5);

return 0;

}

以下是队列标题：

#pragma once
#include "tree.h"

class Queue {

    friend class Tree;

    private:
        typedef struct node {
            Tree::treePtr treeNode;
            node* next;
        }* nodePtr;

        nodePtr head;
        nodePtr current;

    public:  //This is where the functions go
        Queue();
        void push(Tree::treePtr t);
        int pop();
        void print();

};

h：

#pragma once


class Queue;

class Tree{

    friend class Queue;

    private:

        Queue q;

        typedef struct tree {
            int data;
            tree* left;
            tree* right;
        }* treePtr;

        treePtr root;
        int numNodes;


    public:

        Tree();
        void addTreeNode(int integer);

};

这是tree.cpp

This is tree.cpp

#include <cstdlib>
#include <iostream>

#include "Tree.h"
#include "Queue.cpp"


using namespace std;

Tree::Tree() {
    root = NULL;
}

void Tree::addTreeNode(int integer) {
    numNodes++;
    treePtr t = new tree;
    t->left = NULL;
    t->right = NULL;
    t->data = integer;

    cout << "add root\n";
    root = t;
    q.push(t);  
    q.print();

}

推荐答案

您的队列创建树时，编译器需要知道 Queue 类看起来像什么样当 Tree.h 。因此您需要添加

To instantiate your queue upon creation of the Tree, the compiler needs to know what the Queue class looks like when reading Tree.h. So you need to add

#include "Queue.h"

到 Tree.h ，这将使整个 Queue 声明在开始阅读 Tree 之前由编译器可见。

to Tree.h which will make the full Queue declaration visible to the compiler before it starts reading Tree.

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