How can I iterate over an enum?

Question

I just noticed that you can not use standard math operators on an enum such as ++ or += So what is the best way to iterate through all of the values in a C++ enum?

Answer 1

Enumerations are a strange duck :) By default, enumeration are given numeric values starting from 0, but they can be assigned any value and in any order. Given this, you can do something like the following:

#include <iostream>

enum colors {red, blue, green};

int main(int argc, const char * argv[]) {

     

  for (int col=red; col <= green; ++col) {

    switch (col) {

      case red:

        std::cout << "red\n";

        break;

      case blue:

        std::cout << "blue\n";

        break;

      case green:

        std::cout << "green\n";

        break;

    }

  }

  return 0;

}

Output:

red

blue

green

Notice how I used an integer loop variable (since the first enum is assigned value 0).

I could also have equally used:

for (int col=0; col < 3; ++col) ...

But, keep in mind that I could have defined the enum like this:

#include <iostream>

enum colors {red=9, blue=3, green=7};

int main(int argc, const char * argv[]) {

     

  for (int col=0; col < 10; ++col) {

    switch (col) {

      case red:

        std::cout << "red\n";

        break;

      case blue:

        std::cout << "blue\n";

        break;

      case green:

        std::cout << "green\n";

        break;

    }

  }

  return 0;

}

Output

blue

green

red

This is why the switch statement is used to determine the enum values in most cases...

I hope this helps...