c – 如何将istringstream和ifstream分配给istream变量？

std::ifstream file(this->_path)

std::istringstream iss(stringSomething);

std::istream is

基类指针可以指向派生类数据. std :: istringstream和std :: ifstream都是从std :: istream派生的,所以我们可以这样做：

//Note that std::unique_ptr is better that raw pointers
std::unique_ptr<std::istream> stream;

//stream holds a file stream
stream = std::make_unique<std::ifstream>(std::ifstream{ this->_path });

//stream holds a string
stream = std::make_unique<std::istringstream>(std::istringstream{});

现在你只需要使用提取内容

std::string s;
(*stream) >> s;