C++ std::string to Ruby VALUE

Question

How can I convert a C++ std::string object into a Ruby VALUE object?

I tried rb_str_new2(c_string), but it did not work.

I have a function

VALUE foo(){return rb_str_new2(c_string);};

and that gives an error message:

cannot convert ‘std::string {aka std::basic_string<char>}’ to ‘const char*’ for argument ‘1’ to ‘size_t strlen(const char*)’

Why do you call your variable c_string, if it's not a C string? oO — Niklas B.
– Niklas B., Commented Apr 18, 2012 at 15:53

Matheus Moreira · Accepted Answer · 2012-04-18 15:36:07Z

4

You are passing std::string to the function, but it expects a null-terminated const char *.

The std::string::c_str() member function can be used to get one:

rb_str_new_cstr(string.c_str());

answered Apr 18, 2012 at 15:36

Matheus Moreira

17.1k3 gold badges73 silver badges112 bronze badges

Sign up to request clarification or add additional context in comments.

4 Comments

What's the difference between this and rb_str_new2? Can't find much intel about rb_str_new_cstr

@NiklasB, they are the same function. I prefer rb_str_new_cstr because I can infer that the function takes a C string as parameter.

Yes, I thought it might just be a more descriptive alias. Thanks, good to know, will use this in the future :)

@MatheusMoreira Ruby strings and C++ strings can contain zeros. So I would suggest rb_str_new( string.data(), string.size() )