I have a class with a mutex in it:

Class StoreNumbers{
  StoreNumbers();
  AddNumber(size_t number){
    const std::lock_guard<std::mutex> lock(lock_);
    numbers_.push_back(number);
  }

  private:
  std::mutex lock_;
  std::vector<size_t> numbers_;

};

The purpose of the class is to be able to store numbers while used in a multithreaded context. There is certainly better ways to do that but that illustrates my question.

Now I want to have various objects of these classes, in order to store different types of numbers. I also want each of these types to have a different mutex, since they are unrelated.

If I write:

std::vector<StoreNumbers> vec;
vec.push_back(StoreNumber());

I get the compiler error: no matching function for call to 'construct_at', which I understand since the mutex is non copyable.

If instead I use:

std::unique_ptr<std::mutex> lock_=std::make_unique<std::mutex>();

for the lock and dereference it for the lock_guard, I do not get the error anymore. I do not understand why. Thanks for the help!