C ++ 11统一初始化：字段初始化器不是常量

卢卡斯·巴特（Lukas Barth）

我正在尝试实例化一组这样的字符串：

class POI {
public:
...
  static const std::set<std::string> TYPES { "restaurant", "education", "financial", "health", "culture", "other" };
...
}

现在，当我这样做时，我得到这些错误（全部在此行）：

error: field initializer is not constant
 static const std::set<std::string> TYPES { "restaurant", "education", "financial", "health", "culture", "other" };
error: in-class initialization of static data member 'const std::set<std::basic_string<char> > POI::TYPES' of non-literal type
error: non-constant in-class initialization invalid for static member 'POI::TYPES'                                                              
error: (an out of class initialization is required)
error: 'POI::TYPES' cannot be initialized by a non-constant expression when being declared

如果我假设集合中的字符串不被视为const，那对我来说是有道理的。这真的是问题吗？不幸的是，我找不到在初始化程序中将那些字符串声明为const的方法。这可能吗？

塞尔日·桑斯·斯特劳

您必须离线初始化静态变量，如下所示：

#include <set>
#include <string>

class POI {
public:
  static const std::set<std::string> TYPES;
};
const std::set<std::string> POI::TYPES { "restaurant", "education", "financial", "health", "culture", "other" };

这将适用于标准规定的整数/枚举类型（第9.4.2节：）