我是 boost 类型删除的新手,在将对象转换回其原始类型时遇到问题。根据我对 boost 文档的理解,我应该能够使用 boost::any_cast 将类型删除的对象转换回其原始类型,但以下代码因 bad_any_cast 异常而失败。我究竟做错了什么? 非常感谢!
https://www.boost.org/doc/libs/1_67_0/doc/html/boost/any_cast.html
BOOST_TYPE_ERASURE_MEMBER((has_x), x, 0)
namespace bte = boost::type_erasure;
using xConcept = boost::mpl::vector<has_x <float(), bte::_self> ,
bte::copy_constructible<>,
bte::relaxed>;
using AnyXobject = bte::any<xConcept, bte::_self>;
struct xThing{
float x(){
return 4.;
}
float y(){
return 5.;
}
};
int main(){
// instance of concrete implementation
xThing i;
// using concrete implementation to construct type erased object
AnyXobject xconc(i);
// calling x() correctly prints 4
std::cout << xconc.x() << std::endl;
// converting back to concrete implementation fails with boost::bad_any_cast at runtime
auto j = boost::any_cast<xThing>(xconc);
return 0;
}
最佳答案
你需要调用boost::type_erasure::any_cast
修改后的程序如下:
#include <boost/type_erasure/any.hpp>
#include <boost/type_erasure/any_cast.hpp>
#include <boost/type_erasure/member.hpp>
#include <iostream>
BOOST_TYPE_ERASURE_MEMBER((has_x), x, 0)
namespace bte = boost::type_erasure;
using xConcept = boost::mpl::vector<has_x <float(), bte::_self> ,
bte::copy_constructible<>,
bte::relaxed>;
using AnyXobject = bte::any<xConcept, bte::_self>;
struct xThing{
float x(){
return 4.;
}
float y(){
return 5.;
}
};
int main(){
// instance of concrete implementation
xThing i;
// using concrete implementation to construct type erased object
AnyXobject xconc(i);
// calling x() correctly prints 4
std::cout << xconc.x() << std::endl;
// converting back to concrete implementation fails with boost::bad_any_cast at runtime
auto j = bte::any_cast<xThing>(xconc);
return 0;
}
关于c++ - 将 boost 类型删除类型转换回原始类型给我 boost::bad_any_cast,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/50249390/