Converting std::string to std::vector<char>

Question

I am using a library which accepts data as a vector of chars. I need to pass a string to the library.

I think about using std::vector constructor which accepts iterators to carry out the conversion - but wondered if there is a better way of doing it?

/*Note: json_str is of type std::string*/ const std::vector<char> charvect(json_str.begin(), json_str.end());  

Answer 1

Nope, that's the way to do it, directly initializing the vector with the data from the string.

As @ildjarn points out in his comment, if for whatever reason your data buffer needs to be null-terminated, you need to explicitly add it with charvect.push_back('\0').

Also note, if you want to reuse the buffer, use the assign member function which takes iterators.

Answer 2

Your method of populating the vector is fine -- in fact, it's probably best in most cases.

Just so that you know however, it's not the only way. You could also simply copy the contents of the string in to the vector<char>. This is going to be most useful when you either have a vector already instantiated, or if you want to append more data to the end -- or at any point, really.

Example, where s is a std::string and v is a std::vector<char>:

std::copy( s.begin(), s.end(), std::back_inserter(v)); 

As with the constructor case, if you need a null-terminator then you'll need to push that back yourself:

v.push_back('\0');