为什么即使我放了一个 break 语句，我的程序也会一直循环

Question

I am trying to make a log book program but I encountered this problem. It always loops even when there is a break statement.

Here is the part where I use a break statement on while loop but it keeps looping endlessly.

void userPrompt(){
            while(true){
                cout << "[1] Log in\n";
                cout << "[2] Log out\n";
                cout << "[3] View Log Book\n";
                cout << "[0] Exit\n";
                cout << "Choice: ";
                cin >> choice;
                cout << endl;
                switch(choice){
                    case 1:
                        logIn();
                        break;
                    case 2:
                        logOut();
                        break;
                    case 3:
                    viewRecords();
                        break;
                    case 4:
                        break;
                    default:
                        cout<<"Invalid Choice. PLease try again\n";
                        break;
                }
            }
        }

This is the whole code

#include<string>
using namespace std;
struct node{
    string name;
    int timeIn, timeOut;
    node* nextNode;
};
class LogBook{
    private:
        node* head = NULL;
        node* tail = NULL;
        int choice;
    public:
        void userPrompt(){
            while(true){
                cout << "[1] Log in\n";
                cout << "[2] Log out\n";
                cout << "[3] View Log Book\n";
                cout << "[0] Exit\n";
                cout << "Choice: ";
                cin >> choice;
                cout << endl;
                switch(choice){
                    case 1:
                        logIn();
                        break;
                    case 2:
                        logOut();
                        break;
                    case 3:
                    viewRecords();
                        break;
                    case 4:
                        break;
                    default:
                        cout<<"Invalid Choice. PLease try again\n";
                        break;
                }
            }
        }
        void logIn(){
            string name;
            int time;
            node* temp = new node();
            cout << "Enter your name: ";
            cin >> name;
            cout << "Time in: ";
            cin >> time;
            cout << endl;
            temp->name = name;
            temp->timeIn = time;
            temp->nextNode = NULL;
            
            if(head == NULL){
                head = temp;
                tail = temp;
            }
            else{
                tail->nextNode = temp;
                tail = tail->nextNode;
            }
        }
        void logOut(){
            string name;
            int time;
            node* temp;
            temp = head;
            cout << "Enter Name: ";
            cin >> name;
            while(temp != NULL){
                if(temp->name == name){
                    cout << "Time out: ";
                    cin >> time;
                    temp->timeOut = time;
                }
                else
                cout << "Name not found\n";
                    break;
            }
        } 
        void viewRecords(){
            node* temp;
            temp = head;
            while(temp != NULL){
                cout << "\nLog records:\n";
                cout << "Name: " << temp->name << endl;
                cout << "Time in: " << temp->timeIn << endl;
                cout << "Time out: " << temp->timeOut << endl;
                temp = temp->nextNode;
            }
        }
};
int main(){
    LogBook user1;
    user1.userPrompt();
    return 0;
}`

Answer 1

All of your break statements are inside of a switch . So they are breaking out of the switch and back into the while loop (which then loops endlessly).

The switch statement will fall-through to the other case statements unless you place the break , so those break calls are just terminating that particular case.

You need a break statement somewhere in the top-level of your while to signify that you want to stop, since your condition is while(true) . Otherwise it will just loop forever.

Answer 2

You use break statement that is only break switch statement, You need to add break statement for while loop also