将对象传递给类构造函数 [英] Pass an object to a class constructor

问题描述

我有两个类：poly和Node。我创建了一个节点的链接列表，然后我想创建一个新的多边形对象，其中包含指向我的第一个Node对象的指针。

I have two classes: poly and Node. I create a linked list of Nodes, then I want to create a new poly object that contains a pointer to my first Node object.

这里是调用代码：

poly *polyObj = new poly(head);

我已经测试了我的代码，并确认 head包含节点的链接列表，head也为声明为节点*。

I have tested my code and confirmed that "head" contains the linked list of nodes, also head is declared as a Node *.

以下是类定义：

class poly
{
  private:
    Node *start;  
  public:
    poly(Node *head)
    {
      start = head;
    }
};

class Node
{
   private:
    double coeff;
    int exponent;
    Node *next;

  public:
    Node(double c, int e, Node *nodeobjectPtr)
    {
      coeff = c;
      exponent = e;
      next = nodeobjectPtr;
    }
};

我不明白为什么不能将Node *传递给多边形构造函数。

I don't understand why I can't pass a Node * to my poly constructor.

推荐答案

我不明白为什么不能将Node *传递给我的poly构造函数！

I don't understand why I can't pass a Node * to my poly constructor!!

因为 poly 需要知道 Node 是一种类型。您可以通过前向声明来实现：

Because poly needs to know that Node is a type. You can achieve that via a forward declaration:

class Node; // fwd declaration

class poly
{
private:
    Node *start;    
public:
  poly(Node *head)
  {
    start = head;
  }
};

或者，您可以放置​​ Node 类 poly 定义之前的定义。

Alternatively, you can place the Node class definition before poly's definition.

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