How to convert from string to enum value in c++?

Question

I have an enum like this

enum week{Mon, Tue, Wed, Thur, Fri, Sat, Sun};

I am trying to get the index value of the enum by passing a string value.

For example, GetenumIndex("Mon") will return 0.

The prototype of the function is like:

week GetenumIndex(string )

What is the idiomatic way in C++ to implement such a conversion function?

That should be quite easy using a number of `if() else if()` statements. Did you already try that? — user0042, Jul 29 '17 at 12:50
There's something very important that's missing from your question. That would be an actual, specific, question. — Sam Varshavchik, Jul 29 '17 at 12:51
You could use a [map](http://en.cppreference.com/w/cpp/container/unordered_map) that maps a string to an enumeration value. — Some programmer dude, Jul 29 '17 at 12:52
No. There's still no actual programming question anywhere to be found. "Can anyone help me" is not a specific programming question. — Sam Varshavchik, Jul 29 '17 at 13:03
@user8364661 I'd recommend you to accept or adopt my edit, to fix that problem with your question. — user0042, Jul 29 '17 at 13:20
@tobi303 I agree. But aren't duplicates more useful if fomulated in a canonical way? (TBH, instead of that _mentoring_ shit discussed at Meta SO, I believe that editing questions is way more constructive). — user0042, Jul 29 '17 at 13:23
@user0042 if formulated in a canonical way, then yes, but this question isnt so its probably easiest to simply close it — 463035818_is_not_an_ai, Jul 29 '17 at 13:25
@user0042 I dont know what is the Meta opinion an that, but imho it makes more sense to close a low quality question instead of improving it just do flag it as duplicate — 463035818_is_not_an_ai, Jul 29 '17 at 13:26
@tobi303 I referred to my edit, that shaped it into a canonical way. — user0042, Jul 29 '17 at 13:26

user0042 · Answer 1 · 2017-07-29T13:09:41.277

Well, here you go:

#include <iostream>
#include <string>
#include <map>
#include <exception>

enum week{Mon, Tue, Wed, Thur, Fri, Sat, Sun};

week GetenumIndex( const std::string s ) {    
    static std::map<std::string,week> string2week {
       { "Mon", Mon }, 
       { "Tue", Tue },
       { "Wed", Wed }, 
       { "Thur", Thur },
       { "Fri", Fri },
       { "Sat", Sat }, 
       { "Sun", Sun }   
    };
    auto x = string2week.find(s);
    if(x != std::end(string2week)) {
        return x->second;
    }
    throw std::invalid_argument("s");
}

int main() {
    week w = GetenumIndex("Thur");
    std::cout << w << std::endl;
}

See it live here.

@user8364661 Well, closing that question as duplicate was correct. — user0042, Jul 29 '17 at 13:52

How to convert from string to enum value in c++?

1 Answers1