Question

//PROGRAM:
#include<iostream>
#include<conio.h>
using namespace std;
class complex {
private:
    double re, img;
public:
    complex();
    void input();
    complex SubCom(complex c1, complex c2);
    complex SumCom(complex c1, complex c2);
    complex MulCom(complex c1, complex c2);
    void show();
};
complex::complex() {
    re = 0;
    img = 0;
}
void complex::input() {
    cout << "Real:";
    cin >> re;
    cout << "Imagnary:";
    cin >> img;
}
complex complex::SumCom(complex c1, complex c2) {
    re = c1.re + c2.re;
    img = c1.img + c2.img;
}
complex complex::SubCom(complex c1, complex c2) {
    re = c1.re - c2.re;
    img = c1.img - c2.img;
}
complex complex::MulCom(complex c1, complex c2)
{
    re = c1.re * c2.re;
    img = c1.img*c2.img;
}
void complex::show() {
    cout << re << "," << img << "i";

}

int main() {
    complex c1;
    c1.input();
    c1.show();
    complex c2;
    c2.input();
    c2.show();
    complex c;
    c.SumCom(c1, c2);
    c.show();
    c.MulCom(c1, c2);
    c.show();
    c.SubCom(c1, c2);
    c.show();
    _getch();
    return 0;
    system("pause");
}

您好，我制作了一个程序，该程序使用作为类成员的函数将用户的整数转换为整数。我为 sum ， product 和差异做了3个成员函数。现在显示的错误表明

 1. complex::SumCom must return a value 
 2. complex::MulCom must return a value
 3. complex::SubCom must return a value.

Answer 1

这里

head

您已经保证返回一个complex SubCom(complex c1, complex c2); ^^^^^^^ complex SumCom(complex c1, complex c2); ^^^^^^^ complex MulCom(complex c1, complex c2); ^^^^^^^，并且在您的任何成员函数定义中，您都没有返回它。这是 undefined behavior ，您很幸运VS给了您一个编译器错误。关于编译器错误，请尝试启用编译器警告，以查看并挽救自己在代码中的这种未定义行为。

解决方案是向您的成员函数添加一个看起来像（例如complex应该是）的return语句

SumCom()

但是，我建议重载 +, -, * operators ，因为这三个成员函数看起来像是完美的候选者。

这里是example code：

complex complex::SumCom(complex c1, complex c2) 
{
     // implementation
     return /*resulting complex object*/;
}

标准输入：

#include<iostream>

class complex
{
private:
    double re, img;
public:
    complex() = default;

    friend complex operator+(complex c1, const complex& c2) {
        c1.re += c2.re;
        c1.img += c2.img;
        return c1;
    }
    friend complex operator-(complex c1, const complex& c2) {
        c1.re -= c2.re;
        c1.img -= c2.img;
        return c1;
    }
    friend complex operator*(complex c1, const complex& c2) {
        c1.re *= c2.re;
        c1.img *= c2.img;
        return c1;
    }
    void input();
    void show();
};
void complex::input()
{
        std::cout << "Real:" ; std::cin >> re;
        std::cout << "Imaginary:" ; std::cin >> img;
}
void complex::show() {
    std::cout << re << "," << img << "i\n";

}

int main()
{
    complex c1;
    c1.input();
    c1.show();
    complex c2;
    c2.input();
    c2.show();
    complex c = c1 + c2; // now you can
    c.show();
    c = c1 * c2; // now you can
    c.show();
    c = c1 - c2; // now you can
    c.show();
    return 0;
}

输出：

Real:Imaginary:1,1i
Real:Imaginary:2,2i

Answer 2

您必须写 return (object); 当您想返回一些值时。请记住，除非调用某些函数并将返回的值传递给它，否则您返回的值将不会显示在屏幕上（也许是控制台？）。

如何解决类成员函数中的“返回值”错误？

2 个答案: