C++ 面向菜单程序的困难

Question

I am having an issue when trying to use a getline command where a user can enter in a movie and then add to the collection of movies (stored in "movies.txt")

My code is compiling, but it starts out with the 3rd case automatically. When I press "q" to quit that case, it reverts to the menu, yet when I try and write out the file or print the collection, no movie titles have been saved. Where I should go from here? I feel like I'm on the cusp of understanding this.

    #include <iostream>
    #include <string>
    #include <fstream>
    using namespace std;

    const int ARRAY_SIZE = 200;
    string movieTitle [ARRAY_SIZE];
    int loadData (string pathname);
    int writeData (string pathname);
    int getTitle (string movieTitle[]);
    void showAll (int count);

    int main()
    {
        loadData("movies.txt");
        char userInput;
        string movieTitle[ARRAY_SIZE];
        int count = getTitle(movieTitle);

        bool endOfProgram = false;
        while (endOfProgram ==false)
        {
            cout << "1. Read in Collection" << endl;
            cout << "2. Print Collection" << endl;
            cout << "3. Add a Movie to the Collection" << endl;
            cout << "4. Write out Collection" << endl;
            cout << "5. Quit the Program" <<endl;
            cin >> userInput;

            switch(userInput)
            {
                case('1'): 
                {
                    loadData("movies.txt");
                    break;
                }

                case('2'):
                {
                    showAll(loadData("movies.txt"));
                    break;
                }
                case('3'):
                {
                    cout << getTitle(movieTitle);
                    break;
                }
                case('4'):
                {
                    cout <<"Write out Collection" << endl;
                    writeData("movies.txt");
                    break;

                case('5'):
                {
                    endOfProgram=true;
                    cout << "Have a nice day" <<endl;
                    break;
                }
            }
            }
        }
    }
    int loadData (string pathname)
    {
        int count = 0;
        ifstream inFile;
        inFile.open(pathname.c_str());

        if (!inFile)
            return -1;
        else
        {
            while(!inFile.eof())
            {
                getline(inFile, movieTitle[count]);
                count++;
            }
        }
        return count;
    }

    int writeData (string pathname)
    {
        ofstream outfile;
        outfile.open("movies.txt");
        if(!outfile.is_open())
        {
            cout << "Cannot open movies.txt" << endl;
            return -1;
        }

        outfile.close();
        return 0;
    }
    void showAll (int count)
    {
        cout << "\n";
        for (int i=0; i< count; i++)
        {
            cout << movieTitle[i] << endl;
        }
        cout << "\n";
    }

    int getTitle (string movieTitle[])
    {
        string movie;
        int count = 0;

        while(true)
        {
            cout <<"Enter Movie Titles (Type 'q' to quit)" <<endl;
            cin >> movie;
            if (movie == "q")
            {
                break;
            }
            movieTitle [count] = movie;
            count++;
        }
        return count;
    }

Answer 1

I believe cin reads until eol is found, ie the user presses return. So look for integer in the userInput variable, and pass that to your switch statement

int nr = atoi(userInput.c_str())
switch(nr){
    case 1:
    case 2: etc ...

Answer 2

In your codes it is not clear why it directly goes to case '3'. It should wait for a user input first. Seems like something already available in buffer. Just put one cout statement in case '3': and check what it print. If possible put break point there and run the application in debug mode and check the value. Hope this will help you.

     case('3'):
            {
                cout<<"Value of userInput is: "<<userInput<<endl; 
                cout << getTitle(movieTitle);
                break;
            }

Alternately you can add the below line of code just before cin like below

std::cin.clear();
cin >> userInput;

Answer 3

I recommend inputting an integer instead of a character for your input. You will need to change the case values too:

int selection = 0;
//...
cin >> selection;
switch (selection)
{
  case 1: 
  //...
}

You won't have to worry about characters in the buffer. The stream will fail if an integer is not read.