调试时不显示任何内容

Question

可能重复:
如何将对象传递给C++中的函数？

主要课程

#include "List.h"
#include "Car.h"
#include "Worker.h"
#include "Queue.h"
#include <iostream>
#include <string>

using namespace std;
void initWorkerList(List<Worker>);
void initCarList(List<Car>, Queue, Queue);

int main() {
    List<Worker> WorkerList;
    List<Car> CarList;
    Queue q1, q2;
    initWorkerList(WorkerList);
    initCarList(CarList, q1, q2); // Error here
        //..... e.g cout << "Successful!"; but it does not displays it...
}

void initWorkerList(List<Worker> WorkerList) {
    Worker w1 = Worker("Ben Ang", "Ben123", "pass123", 'M');
    WorkerList.add(w1);
    Worker w2 = Worker("Grace Eng", "Gr4ce", "loveGrace", 'W');
    WorkerList.add(w2);
    Worker w3 = Worker("Rebecca Xuan", "Xuanz", "Rebecca Xuan", 'W');
    WorkerList.add(w3);
}

void initCarList(List<Car> CarList, Queue q1, Queue q2) {
    Car c1 = Car("SJS1006Z","Toyota", "Saloon car");
    Car c2 = Car("SFW6666E", "hyundai", "Taxi (Saloon)");
    Car c3 = Car("SCF1006G","Mercedes", "Large Van");
    Car c4 = Car("SBQ1006Z", "Puma", "Saloon Car");

    q1.enqueue(c1);
    q2.enqueue(c1);
    q2.enqueue(c3);
    q1.enqueue(c4);
    q1.enqueue(c1);
    q1.enqueue(c1);
    q1.enqueue(c1);
    q2.enqueue(c2);
    q2.enqueue(c2);
}

完全没有错误.但是在调试时没有显示任何内容......我已经尝试过,我的猜测是initCarList(CarList,q1,q2)有问题; 在该代码之后,其他代码可以工作.它有什么问题吗？谢谢

Answer 1

您是按值而不是按引用传递队列变量.

initCarList(CarList, q1, q2); // Error here

因此initCarList中的任何更改都不会反映回调用者

将您的功能签名更改为

void initCarList(List<Car> CarList, Queue& q1, Queue& q2) {

和声明

void initCarList(List<Car>, Queue&, Queue&);

如果按值传递参数,则其中的任何更改initCarList都是函数作用域的本地更改,并且不会被反射回来.

Pass by Value
Caller              Callee

|------|            |------|
workedList          workedList
| ___  |            | ___  |
||   | |-------->   ||   | | <------
||___| |            ||___| |       |
|      |            |      |       |
|q1    |            |q1    |     (Changing any of these variables 
| ___  |            | ___  |      won't be reflected back)
||   | |-------->   ||   | |       |
||___| |            ||___| |       |
|      |            |      |       |
|q2    |            |q2    |       |
| ___  |            | ___  |       |
||   | |-------->   ||   | |       |
||___| |            ||___| | <------
|______|            |______|


Pass by reference

Caller              Callee

--------            --------
|wList |            |wList |
| ___  |            | ____ |
||   | |-------->   ||    || <------
||___|<|------------||-*__||       |
|   _  |            |      |       |
|q1    |            |q1    |     (Changing any of these variables 
| ___  |            | ____ |       will be reflected back)
||   | |-------->   ||    ||       |
||___|<|------------||-*__||       |
|      |            |      |       |
|q2    |            |q2    |       |
| ___  |            | ____ |       |
||   | |-------->   ||    ||       |
||___|<|------------||-*__|| <------
|______|            |______|