为了序列化任何对象(即对于没有全局ostream& operator<<
的对象,该字符串为空),我创建了一个利用来自单独命名空间的重载std::ostream& operator<<
的函数;
namespace _impl {
template <typename T>
std::ostream& operator<<(std::ostream& osstr, const T& val) {
return osstr;
}
}
template <typename T>
std::string serialize_any(const T& val) {
using namespace _impl;
std::ostringstream osstr;
osstr<< val;
std::string str(osstr.str());
return str;
}
这适用于我尝试的所有类型,除了char的运算符&lt;&lt;被认为是含糊不清的。 我无法理解为什么它适用于int,short或任何其他具有运算符定义的类型,但不适用于chars。有人有什么想法吗?
1>application_src\general_experiments.cpp(39): error C2593: 'operator <<' is ambiguous
1> application_src\general_experiments.cpp(26): could be 'std::ostream &_impl::operator <<<T>(std::ostream &,const T &)'
1> with
1> [
1> T=char
1> ]
1> C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\ostream(914): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,_Elem)' [found using argument-dependent lookup]
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\ostream(827): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,char)' [found using argument-dependent lookup]
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> C:\Program Files (x86)\Microsoft Visual Studio 11.0\VC\include\ostream(742): or 'std::basic_ostream<_Elem,_Traits> &std::operator <<<char,std::char_traits<char>>(std::basic_ostream<_Elem,_Traits> &,char)' [found using argument-dependent lookup]
1> with
1> [
1> _Elem=char,
1> _Traits=std::char_traits<char>
1> ]
1> while trying to match the argument list '(std::ostringstream, const char)'
1> application_src\general_experiments.cpp(52) : see reference to function template instantiation 'std::string serialize_any<char>(const T &)' being compiled
1> with
1> [
1> T=char
1> ]
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
答案 0 :(得分:1)
当重载决议出现时,编译器似乎将const char&
到char
的转换放在与向上转换std::ostringstream
到std::ostream
相同的级别上。
解决方案可能是模拟operator<<
的类型以避免向上转换:
namespace _impl {
template <typename T, typename Y>
Y& operator<<(Y& osstr, const T& val) {
return osstr;
}
}