我有一个指向多态类型的指针, p 。我也有一个 type_info 在同一层次中的某个类, ti 。
I have a pointer to a polymorphic type, p. I also have a type_info for a class somewhere in the same hierarchy, ti.
如果我只是比较 typeid(* p)== ti ,那么我可以在运行时测试指针是否指向一个直接实例。
If I just compare the typeid(*p) == ti, then I can test at runtime whether the pointer is pointing to a direct instance of that class.
是否有类似的方法使用C ++的RTTI来测试 * p inherits
Is there a similar way to use C++'s RTTI to test whether *p inherits from that class?
推荐答案在标准C ++中没有办法做到这一点。如果您使用的实施包含 Itanium C ++ ABI 1 ,你可以这样做,例如:
There's no way to do this in standard C++ alone. If you're using an implementation that has the Itanium C++ ABI1 you can do this though, for example:
#include <iostream> #include <typeinfo> #include <cxxabi.h> #include <memory> class base { protected: base() { } public: static bool check(const std::type_info& p) { // Find the real type_info for single inheritance non virtual const __cxxabiv1::__si_class_type_info* test = dynamic_cast<const __cxxabiv1::__si_class_type_info*>(&p); return test ? typeid(base) == *test->__base_type : false; } virtual ~base() {} }; class der : public base { }; class foo {}; int main() { der d; foo f; std::cout << base::check(typeid(d)) << "\n"; std::cout << base::check(typeid(f)) << "\n"; }在这里,这是因为类型有一个单一的非精确继承的基。你可以支持更多的情况,但要小心和类似 dynamic_casts 。
Here this works because the type has a single, non-virtuallly inherited base. You can support more cases though with care and similar dynamic_casts.
虽然这是可能的,你解决了错误的问题虽然 - 基于 std :: map 的解决方案是更便携,避免依赖于这样的实现细节。
Whilst this is possible under these certain circumstances I think you're solving the wrong problem though - a solution based around a std::map is more portable and avoids relying on implementation details like this.
1 混淆地命名,它是一个惊人的大型编译器/体系结构列表,而不仅仅是Itanium
1 confusingly named, it's a surprisingly large compiler/architecture list, not just Itanium
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