"将 std::string 转换为 std::vector<char>"

Question

I am using a library which accepts data as a vector<\/code> of char<\/code> s. I need to pass a string<\/code> to the library.

/*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');

Answer 3

An alternative that might be worth considering if you need the terminating null is:

std::vector<char> charvect(json_str.c_str(), json_str.c_str() + json_str.size() + 1); 

and if charvect already exists you can do:

charvect.assign(json_str.c_str(), json_str.c_str() + json_str.size() + 1);

This might be quicker than doing a push_back('\\0') particularly if the push_back triggers a memory reallocation.

Answer 4

You can do it in this way.

  std::string s = "Hello World!";
    std::vector<char> v(s.begin(), s.end());
    for (const char &c: v)
        std::cout << c;