#include #include template class JISingleTon_CallOnce { public: static _Class& get_instance() { std::call_once(&flag_, [&ptr]() { ptr_ = std::make_unique(); }); return *instance; } JISingleTon_CallOnce = default; virtual ~JISingleTon_CallOnce() = default; JISingleTon_CallOnce(const JISingleTon_CallOnce&) = delete; JISingleTon_CallOnce& operator=(const JISingleTon_CallOnce&) = delete; JISingleTon..