问题
I want to avoid the usage of sprintf in my C++ code so I can use only std strings from C++, but I haven't found the way to replace it yet. I currently use sprintf to format dates and times like this:
char myDate[DATE_LENGTH]{};
sprintf(myDate, "%4d-%02d-%02d %02d:%02d:%02d", year, month, day,
hour, minute, second);
In this way, I will get a fixed length for each integer, with leading zeros if needed.
I have searched how to replace this with stringstream, and found this:
std::ostringstream ss;
ss << std::setw(5) << std::setfill('0') << 12 << "\n";
But this only would format one of the integers. I would need to do this for each date and tiem component and then append all of them together. So to replace one line of C-style code, I would need much more new code.
Is not there any way to do better than this?
回答1:
(1) Define your own datatime class.
(2) Define the operator <<() and operator >>() for it. In these function, use std::time_put and std::time_get facet to implement.
(3) If the std::time_put and std::time_get can't satisfy your needs, you can define your own time_put/get facet by inheriting them, and other assistant facet such as date_time format manager if necessary.
PS: If you're using c++11, std::time_put::put() and std::time_get::get() may be satisfied.
Good Luck!
回答2:
There is nothing bad in using snprintf() or strftime() in a C++ application. They are fast, reliable, and they are part of the standard library. IOStreams are sometimes just too verbose to use them directly. You can always wrap the sprintf-based serializer into an iostream shell.
Another way to format date/time in C++11 without boilerplate is via put_time.
来源：https://stackoverflow.com/questions/22142372/formatting-dates-with-stringstream