Switch statement??

[mermaidly]

Hi guys, I'm putting a switch statement in a loop, for example with 3 cases as below. How do I make sure that in order to proceed with the 3rd case, 1st and 2nd options were chosen beforehand, and both containing correct values inside?

  do{
        cout << "1. Select first colour" << endl;
        cout << "2. Select second colour" << endl;
        cout << "3. Mix the colours" << endl;
        cout << "0. Exit" << endl; 
        cout << "Option: ";
        cin >> option;

        string colour1, colour2, colour3;
        switch(option){
            case 1:
                cout << "First colour: ";
                cin >> colour1;
                break;
        
            case 2:
                cout << "Second colour: ";
                cin >> colour2;
                break;
        
            case 3:
                if( ???? ){
                   cout << "Final colour is: " << colour3;
                }
                break;
        
            default:
                cout << "Error!" << endl; 
                break;
    
        }
        
    }while(option != 0);

[AbstractionAnon]

How about something like this:

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

string get_color()
{
    string color;
    
    cin >> color;
    //  perform whatever editing you want here
    //  if good then return color
    //  else return empty string
}

int main()
{
    int option;
    do {
        cout << "1. Select first colour" << endl;
        cout << "2. Select second colour" << endl;
        cout << "3. Mix the colours" << endl;
        cout << "0. Exit" << endl;
        cout << "Option: ";
        cin >> option;

        string colour1, colour2, colour3;
        switch (option) {
        case 1:
            cout << "First colour: ";
            colour1 = get_color();
            break;

        case 2:
            cout << "Second colour: ";
            colour2 = get_color();
            break;

        case 3:
            if (colour1.empty() || colour2.empty())
            {   //  error
                continue;
            }
            //  calculate colour3
            cout << "Final colour is: " << colour3;            
            break;

        default:
            cout << "Error!" << endl;
            break;
        }
    } while (option != 0);
    return 0;
}

[dhayden]

Don't use a switch statement. You expect to input one number, then another, then print the final color. There's no reason for a loop or switch statement. This is straight-line code.