C ++我在哪里把if语句放在类或对象中来验证人口的出生和死亡

Question

我需要在我的计划中验证我的Population，birth和death。我希望Population始终开始，永远不会被允许低于2。对于birth和death，我从不希望它们小于0。我该如何完成这项任务？如果您需要任何澄清，我可以提供。我是这个网站的新手。

#include <iostream>
#include <cmath>
#include <iomanip>
#include <string>
using namespace std;



class Population
{
private:
    int current_pop;
    int Births;
    int annuel_births;
    int deaths;
    int annuel_deaths;
public:

    void setpop(int);
    int getpop(int);
    void setborn(double);
    void setdead(double);
    double getdead(float deaths, int current_pop)
    {
        return deaths / current_pop;
    };
    double getborn(float Births, int current_pop)
    {
        return Births / current_pop;
    };
};
void menu();
void Population::setpop(int people)
{

    current_pop = people;
    if (people < 2)
    {
        people = 2;
    }
}
int Population::getpop(int people)
{
    return current_pop;
}

void Population::setborn(double baby)
{
    Births = baby;
    if (baby < 0)
    {
        baby = 0;
    }
}

void Population::setdead(double dead)
{
    deaths = dead; // i tried to add the validation here but it still allows me to change it //below 0 same thing with the other validations
    if (dead < 0)
    {
        dead = 0;
    }

}

int main()
{
    double Births = 0;
    double  Deaths = 0;
    int people = 2;
    Population location;
    char choice;

    cout << "Welcome to the population program.\nPlease select one of the menu items by entering a value 1-8.   \n1 . Enter population, Annuel Births, Annuel Deaths.\n2 . Change Population.\n3 . Change Annuel Births.\n4 . Change annuel Deaths.\n5 . View current Population.\n6 . View Birthrate.\n7 . View DeathRate. \n8 . exit program." << endl;

    do
    {
        const char Max_Choice = '8';
        char getChoice(char);
        choice = getChoice(Max_Choice);
        switch (choice)
        {
        case '1': cout << "This is the town of Kakariko Village.\nPlease input the current population: "; cin >> people;

            cout << "input the annuel number of births: "; cin >> Births;
            cout << "input the annuel deaths in this village: "; cin >> Deaths;
            cout << "==========================================" << endl;
            menu();
            char getChoice(char);
            break;

        case '2': cout << "ok you wish to change population!\nThis is the town of Kakariko Village.\nPlease input the current population: "; cin >> people;
            cout << " " << endl;
            menu();
            char getChoice(char);
            location.setpop(people); // calling function with variable as argument
            cout << "current populaion = " << people << endl;
            break;
        case '3': cout << "you wish to change the number of annuel births\ninput the annuel number of births: "; cin >> Births;
            location.setborn(Births);
            cout << "your birthrate is: " << Births << endl;
            cout << " " << endl;
            menu();
            char getChoice(char);
            break;

        case '4': cout << "ok you wish to change the annuel number of deaths\ninput the annuel deaths in this village: "; cin >> Deaths;
            location.setdead(Deaths);
            cout << " your death rate is: " << Deaths << endl;
            cout << " " << endl;
            menu();
            char getChoice(char);
            break;
            location.setpop(people);
        case'5': cout << "ok you wish to view population it's: " << people << endl;
            break;

        case'6':cout << "ok you wish to view the birthrate it's: " << location.getborn(Births, people) << endl; 
            cout << " " << endl;
            menu();
            char getChoice(char);
            break;

        case'7':cout << "ok you wish to view the deathrate it's: " << location.getdead(Deaths, people) << endl;
            cout << " " << endl;
            menu();
            char getChoice(char);
            break;
        case'8': 
                return 0;
            break;

        }
    } while (choice != '8'|| choice != '1'); cin >> choice;

    system("pause");
    return 0;
}



char getChoice(char max)
{
    char choice = cin.get();
    cin.ignore(256, '\n');
    cin.clear();
    while (choice < '1' || choice > max)
    {
        cout << "choice must be between 1 and " << max << ". "
            << "enter choice again.: "; choice = cin.get();
        cin.ignore();
    }
    return choice;


}

void menu()
{
    cout << "Please select one of the menu items by entering a value 1-8.   \n1 . Enter population, Annuel Births, Annuel Deaths.\n2 . Change Population.\n3 . Change Annuel Births.\n4 . Change annuel Deaths.\n5 . View current Population.\n6 . View Birthrate.\n7 . View DeathRate. \n8 . exit program." << endl;
}

Answer 1

检查您的功能setDead()

void Population::setdead(double dead)
{
    deaths = dead; 
    // i tried to add the validation here but it still allows me to change it 
    //below 0 same thing with the other validations
    if (dead < 0) // ???
    {
        dead = 0; // ???
    }
}

您实际上正在更改函数的参数，而您应该验证类的数据成员。