C++: Print out enum value as text

Question

If i have an enum like this

enum Errors {ErrorA=0, ErrorB, ErrorC}; 

Then i want to print out to console

Errors anError = ErrorA; cout<<anError;/// 0 will be printed 

but what i want is the text "ErrorA", can i do it without using if/switch?
And what is your solution for this?

Answer 1

Using map:

#include <iostream> #include <map> #include <string>  enum Errors {ErrorA=0, ErrorB, ErrorC};  std::ostream& operator<<(std::ostream& out, const Errors value){     static std::map<Errors, std::string> strings;     if (strings.size() == 0){ #define INSERT_ELEMENT(p) strings[p] = #p         INSERT_ELEMENT(ErrorA);              INSERT_ELEMENT(ErrorB);              INSERT_ELEMENT(ErrorC);              #undef INSERT_ELEMENT     }         return out << strings[value]; }  int main(int argc, char** argv){     std::cout << ErrorA << std::endl << ErrorB << std::endl << ErrorC << std::endl;     return 0;    } 

Using array of structures with linear search:

#include <iostream> #include <string>  enum Errors {ErrorA=0, ErrorB, ErrorC};  std::ostream& operator<<(std::ostream& out, const Errors value){ #define MAPENTRY(p) {p, #p}     const struct MapEntry{         Errors value;         const char* str;     } entries[] = {         MAPENTRY(ErrorA),         MAPENTRY(ErrorB),         MAPENTRY(ErrorC),         {ErrorA, 0}//doesn't matter what is used instead of ErrorA here...     }; #undef MAPENTRY     const char* s = 0;     for (const MapEntry* i = entries; i->str; i++){         if (i->value == value){             s = i->str;             break;         }     }      return out << s; }  int main(int argc, char** argv){     std::cout << ErrorA << std::endl << ErrorB << std::endl << ErrorC << std::endl;     return 0;    } 

Using switch/case:

#include <iostream> #include <string>  enum Errors {ErrorA=0, ErrorB, ErrorC};  std::ostream& operator<<(std::ostream& out, const Errors value){     const char* s = 0; #define PROCESS_VAL(p) case(p): s = #p; break;     switch(value){         PROCESS_VAL(ErrorA);              PROCESS_VAL(ErrorB);              PROCESS_VAL(ErrorC);     } #undef PROCESS_VAL      return out << s; }  int main(int argc, char** argv){     std::cout << ErrorA << std::endl << ErrorB << std::endl << ErrorC << std::endl;     return 0;    } 

Answer 2

Use an array or vector of strings with matching values:

char *ErrorTypes[] = {     "errorA",     "errorB",     "errorC" };  cout << ErrorTypes[anError]; 

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EDIT: The solution above is applicable when the enum is contiguous, i.e. starts from 0 and there are no assigned values. It will work perfectly with the enum in the question.

To further proof it for the case that enum doesn't start from 0, use:

cout << ErrorTypes[anError - ErrorA];