C++ - 如何制作一个简单的计时器，我将如何使用基于它的 if 语句？

Question

我正在制作一种虚拟宠物。在某种程度上，我在复制电子鸡。

// VirtualPetProjClassesandObjectsPRCT.cpp : Defines the entry point for the console application.
//
#include "stdafx.h"
#include <iostream>
#include <string>
#include <cmath>
#include "Vpet.h"

int main()
{
    // Set Name & General Info
    std::string pop;
    std::cout << "What would you like to call your pet?" << std::endl;
    std::cin >> pop;
    std::cout << "List of commands you can do with " << pop << std::endl << "'state'" << std::endl << "'quit'" << std::endl << "'feed'." << std::endl;
    std::cout << "If you feed bob less than quarter his weight he will gain weight but still be hungry!" << std::endl;
    std::cout << "Bob weighs 50 kgs!" << std::endl;

    VPet bob(50, false);
    bob.feedPet(5);
    do
    {
        //input
        std::string input;
        std::cin >> input;

        if (input == "Quit" || input == "quit")
        {
            return 0;
        }

        if (input == "Feed" || input == "feed")
        {
            std::cout << "Enter the amount you would like to feed " << pop << " - ";
            int x;
            std::cin >> x;
            if (x > (bob.getWeight() * 0.5))
            {
                std::cout << "Bob can't eat that much!" << std::endl;
            }
            else
            {
                bob.feedPet(x);
                std::cout << "You have fed " << pop << " " << x << " kgs of food!" << std::endl;
            }
        }

        // State
        if (input == "State" || input == "state")
        {
            std::cout << pop << " weighs: " << bob.getWeight() << std::endl;

            if (bob.getHungry())
            {
                std::cout << pop << " is hungry." << std::endl;
            }
            else
            {
                std::cout << pop << " is not hungry." << std::endl;
            }
        }
    } while (0 != 1);
}

我创建了一个类和一些函数来喂养宠物，检查它的重量以及他是否饿了，但我还想制作一个时钟，每隔几分钟或几秒钟就会检查一下时间过去了多少，是否一定数量过去了，我会使用我之前定义的 bool 变量打印出虚拟宠物饿了。谢谢。

Answer 1

您可以使用库 chrono 来测量时间跨度，然后采取相应的行动。

#include <chrono>
#include <ctime>
#include <iostream>
#include <thread>

int main () { 
    auto start = std::chrono::system_clock::now();

    while (1) {
        std::this_thread::sleep_for(std::chrono::milliseconds(100));

        // In your real code you will perhaps not need the sleep

        const auto now = std::chrono::system_clock::now();
        const auto duration = now - start;
        if ( duration.count() > 2e9) {
            break;
        }

        std::cout << "waiting ..."  << std::endl;
    } 

    std::cout <<"done" << std::endl;
}

time ./chrono_example 这个输出:

等待...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...等待 ...完成

真正的 0m2.013s

用户 0m0.002s

系统 0m0.004s