I intend to have a class which has an inner class and a method with similar names. The code of example1.cpp compiles with no problem even though I have the an inner class and a method with the same name B. While example2.cpp will not work if I rename Position to position with small letters. In such a case, the position() method and the position class conflict with each other and I receive:
error: ‘ObjType::position<false> ObjType::position() const’ conflicts with a previous declaration
inline auto position() const->class position<false>{return {*this};}
^
compilation terminated due to -Wfatal-errors.
What is the difference between these two classes? Why the latter one is giving error but not the former one?
g++ -std=c++11 test2.cpp -Wall -Wextra -Wfatal-errors && ./a.out
.
// example1.cpp
#include <iostream>
class A
{
public:
friend class B;
class B
{
public:
int x;
void show() {std::cout<<"x: "<<x<<std::endl;}
B(): x(6) {}
};
B B()
{
class B b;
return b;
}
};
int main()
{
A a;
a.B().show();
return 0;
}
.
// example2.cpp
#include <iostream>
#include <iostream>
#include <iostream>
#include <type_traits>
class Point
{
public:
double x,y,z;
void print() const
{
std::cout<<"x:"<<x<<", y:"<<y<<"z:"<<z<<std::endl;
}
};
class ObjType
{
template<bool> friend class Position;
Point data;
public:
template<bool ByRef>
class Position
{
typename std::conditional<ByRef,ObjType&,ObjType const&>::type ref;
public:
inline Position(typename std::conditional<ByRef, ObjType&, ObjType const&>::type ref) : ref(ref) {}
inline Position(const Point &ref): ref(ref){}
inline auto operator =(Point const& a)->Position&{ref.data.subvec(0,2)=a; return *this;}
inline auto operator =(Point&& a)->Position&{data=a; return *this;}
inline void print() const{ref.data.print();}
};
inline ObjType(const Point &data): data(data){}
inline void print() const{data.print();}
/*error > */ inline auto position() const->class Position<false>{return {*this};}
inline auto position()->class Position<true>{return {*this};}
};
int main()
{
ObjType obj({1.1,1.2,1.3});
std::cout<<"****************"<<std::endl;
std::cout<<"obj.print() :"<<std::endl;
obj.print();
std::cout<<"obj.position.print() :"<<std::endl;
obj.position().print();
std::cout<<"****************"<<std::endl;
return 0;
}
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