C ++ stl方法从字符串中提取子字符串 - >到（像Javascript子字符串）

Question

我试图在功能上复制JavaScript的子字符串，通过给定from / to pos的子字符串from / to字符串中提取字符串。 我应该怎样继续以后我肠道的位置，此功能from和to ？

std::string& UT::extractid(std::string& url)
{
    std::vector< std::string > tokens;
    std::string id = "";
    tokens = split(url,'v=');
    video_id = tokens.at(1);
    if(video_id.length()>2)
    {
        string::size_type ampersandPosition = video_id.find('&', 0 );
        if( ampersandPosition != string::npos ) {
            cout << "Found  at " << loc << endl;
        } else {
            cout << "Didn't find  " << endl;
        }
    }
    return video_id;
}

Answer 1

代替

return video_id;

做这个：

size_t start = video_id.find_first_of("/");
if (start == string::npos) start = 0;
assert(ampersandPosition > start);
return video_id.substr(start, ampersandPosition - start);