从基类继承和选择构造函数

Question

我的问题很简单，但我被卡住了。如何从基类中选择所需的构造函数？

// node.h
#ifndef NODE_H
#define NODE_H

#include <vector>

// definition of an exception-class
class WrongBoundsException
{
};

class Node
{
    public:
        ...

        Node(double, double, std::vector<double>&) throw (WrongBoundsException);
        ...
};

#endif


// InternalNode.h
#ifndef INTERNALNODE_H
#define INTERNALNODE_H

#include <vector>
#include "Node.h"


class InternalNode : public Node
{
    public:
        // the position of the leftmost child (child left)
        int left_child;
        // the position of the parent
        int parent;

        InternalNode(double, double, std::vector<double>&, int parent, int left_child) throw (WrongBoundsException);

    private:
        int abcd;

};

#endif


// InternalNode.cpp

#include "InternalNode.h"

#define UNDEFINED_CHILD -1
#define ROOT -1


// Here is the problem
InternalNode::InternalNode(double a, double b, std::vector<double> &v, int par, int lc) 
throw (WrongBoundsException)
: Node(a, b, v), parent(par), left_child(lc)
{
    std::cout << par << std::endl;
}

我明白了：

$ g++ InternalNode.cpp

InternalNode.cpp:16: 错误：'InternalNode::InternalNode(double, double, std::vector >&, int, int) throw (WrongBoundsException)' 的声明抛出不同的异常 InternalNode.h:17：错误：来自先前的声明'InternalNode::InternalNode(double, double, std::vector >&, int, int)'

更新 0：修复缺失：

更新 1：修复抛出异常

Answer 1

此简化代码编译正确，但由于缺少基类的构造函数定义而无法链接：

#include <vector>

// definition of an exception-class
class WrongBoundsException {
};

class Node {
    public:
        Node(double, double, std::vector<double>&) 
                throw (WrongBoundsException);
};

class InternalNode : public Node {
    public:
        // the position of the leftmost child (child left)
        int left_child;
        // the position of the parent
        int parent;

        InternalNode(double, double, std::vector<double>&, 
                        int parent, int left_child) 
                        throw (WrongBoundsException);
    private:
        int abcd;

};

// Note added exception specification
InternalNode::InternalNode(double a, double b, 
                            std::vector<double> &v, 
                    int par, int lc) throw (WrongBoundsException)
        : Node(a, b, v), parent(par), left_child(lc)
{
}

顺便说一句，您为什么觉得需要使用异常规范？在 C++ 中，它们通常看起来有点浪费时间。

Answer 2

您缺少构造函数定义的异常规范：

InternalNode::InternalNode(double a, double b, std::vector<double> &v, int par, int lc) 
  throw (WrongBoundsException)
  : Node(a, b, v), parent(par), left_child(lc)
{
    std::cout << par << std::endl;
}