需求：一个 Log 接口，可以生成 容易解析的 输出，然后不用有太多功能了。结果我搞了个有六个参数的模板，叫做
"Logger"，有三个参数是必需的：输入类型 LogItem，输出类型 CString，一个 Level 类型。可是这个 Level
类型不加也可以，函数参数加个 level 枚举就可以了，加上了的结果就是下面的乱七八糟：感觉是完全失掉了模板的本意 :(
template<ILogPolicy::Level level>
class Level_traits
{
public:
enum{value = level};
typedef Level_traits<level> type;
static LPCTSTR name;
};
typedef Level_traits<ILogPolicy::LEVEL_ALL> LEVEL_ALL;
LPCTSTR LEVEL_ALL::name = _T("NOTIFICATION");
typedef Level_traits<ILogPolicy::LEVEL_VERBOSE> LEVEL_VERBOSE;
LPCTSTR LEVEL_VERBOSE::name = _T("DEBUG");
typedef Level_traits<ILogPolicy::LEVEL_INFO> LEVEL_INFO;
LPCTSTR LEVEL_INFO::name = _T("INFO");
typedef Level_traits<ILogPolicy::LEVEL_WARNING> LEVEL_WARNING;
LPCTSTR LEVEL_WARNING::name = _T("WARNING");
typedef Level_traits<ILogPolicy::LEVEL_FATAL> LEVEL_FATAL;
LPCTSTR LEVEL_FATAL::name = _T("FATAL");
template<class LogItem>
void LogT(const LogItem& item)
{
switch(item.eLevel)
{
case ILogPolicy::LEVEL_FATAL:
typedef LEVEL_FATAL LEVEL;
Logger<LogItem, CString, LEVEL_FATAL>::WriteLog(item);
break;
case ILogPolicy::LEVEL_WARNING:
Logger<LogItem, CString, LEVEL_WARNING>::WriteLog(item);
break;
case ILogPolicy::LEVEL_INFO:
Logger<LogItem, CString, LEVEL_INFO>::WriteLog(item);
break;
case ILogPolicy::LEVEL_VERBOSE:
Logger<LogItem, CString, LEVEL_VERBOSE>::WriteLog(item);
break;
case ILogPolicy::LEVEL_ALL:
Logger<LogItem, CString, LEVEL_ALL>::WriteLog(item);
break;
}
}
