用C ++写入函数内部的ostream

Question

consider the following function:

void writer(ofstream &output) {
output << "a string to write" << endl;

}

but when i try to call this, i get an error that '<<' is not defined. how can I fix this?

Answer 1

Add #include <fstream> or change ofstream to ostream

Most likely you lack an include, so that ofstream is only forward declared.