Question

我在尝试为我的子类实现构造函数时遇到了困难。我理解构造函数的目的是将类的状态设置为传递的值？我在这是否正确？

我收到错误;

没有匹配功能可以调用超级＆＃39;

我的问题是我是否必须将子类的构造函数链接到超类？两个类之间的构造函数之间的关系是什么？

#include<iostream>
using namespace std;

class Buildings
{

private:

    float price, area;
    string city;


public:

    Buildings(float, float, string);
   // Buildings(float, float, float);
    void virtual display();
    void virtual getprice(float);
    void virtual getcity(string);
    void virtual getarea(float);

};

Buildings::Buildings(float b_price, float b_area, string b_city):price(b_price), area(b_area), city(b_city)
{

}

void Buildings::display()
{

    cout<<"The city, price and area(sqft) of the building are: "<<city<<endl<<price<<endl<<area;
}

void Buildings::getprice(float aprice)
{

    price = aprice;//potential error handling

}

void Buildings::getarea(float asize)
{
    area = asize;
}

void Buildings::getcity(string acity)
{
    city  = acity;
}



class Apartment:public Buildings
{


private:
    float numtennants;
    float rent;
    float rentpr;

public:

    Apartment(float numres, float numrent, float numrentpr);
    void virtual display();
    void virtual avgrent(float);
    void virtual totrent(float);
    void virtual totres(float);

};

Apartment::Apartment(float numres, float numrent, float numrentpr):numtennants(numres),rent(numrent),rentpr(numrentpr)
{}

void Apartment::display()
{
    Buildings::display();

}

Answer 1

您必须在子类member initializer list中调用父类的构造函数。

struct A {
  A(int a) : a_(a) {}
  int a_;
};

struct B : public A {
  B(int a, int b) : A(a), b_(b) {}
  int b_;
};

Answer 2

Buildings没有默认构造函数。您必须显式调用唯一存在的Buildings构造函数，并传递适当的参数。

如果你想要禁止公共默认构造Buildings对象，但允许子类使用它，你可以创建一个protected的默认构造函数。像

class Buildings
{
public:
    // Public constructor, only way to construct object of this class
    // for the general public
    Buildings(float, float, string);

    // Other public functions...

protected:
    // Default constructor, which initializes the private members
    // to some suitable values
    // Only usable by child-classes
    Buildings()
        : price(0), area(0), city("")
    {}

private:
    float price, area;
    string city;
};

如何在子类中定义构造函数

2 个答案: