提升日期时间转换错误

Question

我从synaptic安装了boost。

现在我需要将日期从/转换为字符串，但是当我编写如下代码时，

date dt{2018-9-14};

string str=to_simple_string(dt);

cout<<str<<endl;

它出错了：

/usr/include/boost/date_time/date_formatting.hpp:44: undefined reference to `boost::gregorian::greg_month::as_short_string() const'
/usr/include/boost/date_time/date_formatting.hpp:49: undefined reference to `boost::gregorian::greg_month::as_long_string() const'

我该怎样解决这个问题？

Answer 1

As the other answer stated, the constructor is wrong (use commas, or you'll simply say 2018-9-14 which is equal to 1995).

Next, you forgot to link the boost_date_time library:

Starting from a completely new and fresh 16.04 machine:

apt update; apt install -yy build-essential libboost-all-dev
echo -e '#include <boost/date_time.hpp>\nint main(){std::cout<<boost::gregorian::to_simple_string({2018,9,14})<<std::endl;}' > test.cpp
g++ -std=c++11 test.cpp -lboost_date_time && ./a.out 

Works and prints

2018-Sep-14

Teach a man how to fish: What is an undefined reference/unresolved external symbol error and how do I fix it?

Show a man eating the fish:

Answer 2

你的dt初始化看起来很可疑。如果你想要2018年9月14日，我想你想要{2018,9,14}。

您的代码的更完整版本可能如下所示：

#include <boost/date_time.hpp>

int main(int argc, char* argv[]) {
  const boost::gregorian::date dt{2018, 9, 14};
  const std::string str = boost::gregorian::to_simple_string(dt);

  std::cout << str << std::endl;

  return 0;
}

正确生成

2018-Sep-14

作为输出。