How to pass std::cin to a class constructor? - c++

Question

I am trying to create a class which can read input from either a file stream or std::cin:
#include <string>
#include <iostream>
#include <mutex>
class A
{
public:
explicit A(std::istream& input)
: input_(input)
{
;
}
public:
void doSomething()
{
std::string word;
while (input_ >> word) {
std::cout << word << std::endl;
}
}
private:
std::istream& input_;
std::mutex mutex_;
};
int main()
{
auto a = A(std::cin);
a.doSomething();
return 0;
}
But the compiler gives the following output:
~/test/main.cpp: In function ‘int main()’:
~/test/main.cpp:31:22: error: use of deleted function ‘A::A(A&&)’
auto a = A(std::cin);
^
~/test/main.cpp:5:7: note: ‘A::A(A&&)’ is implicitly deleted because the default definition would be ill-formed:
class A
^
~/test/main.cpp:5:7: error: use of deleted function ‘std::mutex::mutex(const std::mutex&)’
In file included from /usr/include/c++/7/mutex:43:0,
from ~/test/main.cpp:3:
/usr/include/c++/7/bits/std_mutex.h:97:5: note: declared here
mutex(const mutex&) = delete;
^~~~~
How should I fix the error? Or generally, how do we create a class that can read input either from a file stream or std::cin?
Edit
Initially I tried to reduce the amount of code as much as possible, and in that process, I removed std::mutex part, which gave a very different compiler output. Plus, there was a typo where input_ was std::stream and #JerryJeremiah was correct in the first comment that it should be std::istream &.
Now, I think the question doesn't quite match the problem, as #acraig5075 also pointed out in the comment. And there are similar questions on Stack Overflow already, so I'm going to delete my question.

Answer 1

I found the answer.
std::mutex is not copyable, and the class containing it becomes not-copyable as well.
The code should be:
int main()
{
A a(std::cin);
a.doSomething();
return 0;
}