c++ - 对 `SavingsAccount::annualInterestRate' 的 undefined reference

Question

我在编译我的 C++ 代码时偶然发现了这个错误。这是我的代码:

#include<iostream>
#include<iomanip>

using namespace std;

class SavingsAccount
{
private:
    static float annualInterestRate;
    float savingBalance;

public:
    float calculateMonthlyInterest()
        {return savingBalance+=(savingBalance*annualInterestRate)/12;}//adding the interest to savingBalance

    static void modifyInterestRate(float r)
    {annualInterestRate=r;}//modify the annualInterestRate

    SavingsAccount(float saving)//constructor with argument to set savingValue
    {savingBalance=saving;}

};


int main()
{
SavingsAccount saver1(2000.00), saver2(3000.00);//instantiate 2 different SavingsAccount object

SavingsAccount::modifyInterestRate(0.03);//set new interest to 3%
//printing savers' new balance after 3% interest applied
cout<<"THIS MONTH (3% INTEREST) :\n";
cout<<fixed<<setprecision(2)<<"Saver 1 balance : RM "<<saver1.calculateMonthlyInterest();
cout<<"\nSaver 2 balance : RM "<<saver2.calculateMonthlyInterest();

SavingsAccount::modifyInterestRate(0.04);//set new interest to 4%
//printing savers' new balance after 4% interest applied
cout<<"\n\nNEXT MONTH (4% INTEREST) :\n";
cout<<"Saver 1 balance : RM "<<saver1.calculateMonthlyInterest();
cout<<"\nSaver 2 balance : RM "<<saver2.calculateMonthlyInterest();

return 0;

完整的错误信息:C:\Users\NURULA~1\AppData\Local\Temp\ccOIgGs2.o 类练习 3 no 1 ver 2.cpp:(.rdata$.refptr._ZN14SavingsAccount18annualInterestRateE[.refptr._ZN14SavingsAccount18annualInterestRateE]+0x0): undefined reference ` SavingsAccount::annualInterestRate'

这张照片是我正在尝试做的问题的快照:

这个问题并没有要求制作一个构造函数，但我做了一个，假设我需要初始化余额值，但我有点感觉这就是导致问题和错误消息的原因。我对吗？ ....还是错误的？

先谢谢你。

Answer 1

您需要在某处定义 annualInterestRate 变量，其中:

float SavingsAccount::annualInterestRate;

静态变量就像全局变量；它们有单独的声明和定义。