ワウ。 C++は奇妙なことで私を驚かせることは決してありません。狂気のちょうどすべての種類のです
In a template definition, unqualified names will no longer find members of a dependent base (as specified by [temp.dep]/3 in the C++ standard). For example,
template <typename T> struct B {
int m;
int n;
int f();
int g();
};
int n;
int g();
template <typename T> struct C : B<T> {
void h()
{
m = 0; // error
f(); // error
n = 0; // ::n is modified
g(); // ::g is called
}
};
You must make the names dependent, e.g. by prefixing them with this->. Here is the corrected definition of C::h,
template <typename T> void C<T>::h()
{
this->m = 0;
this->f();
this->n = 0
this->g();
}
As an alternative solution (unfortunately not backwards compatible with GCC 3.3), you may use using declarations instead of this->:
template <typename T> struct C : B<T> {
using B<T>::m;
using B<T>::f;
using B<T>::n;
using B<T>::g;
void h()
{
m = 0;
f();
n = 0;
g();
}
};
。ありがとう、ダビデ。
はここで、標準の "temp.dep/3" セクションの[ISO/IEC 14882:2003]:
In the definition of a class template or a member of a class template, if a base class of the class template depends on a template-parameter, the base class scope is not examined during unqualified name lookup either at the point of definition of the class template or member or during an instantiation of the class template or member. [Example:
typedef double A;
template<class T> class B {
typedef int A;
};
template<class T> struct X : B<T> {
A a; // a has typedouble
};
The type name A
in the definition of X<T>
binds to the typedef name defined in the global namespace scope, not to the typedef name defined in the base class B<T>
. ] [Example:
struct A {
struct B { /* ... */ };
int a;
int Y;
};
int a;
template<class T> struct Y : T {
struct B { /* ... */ };
B b; //The B defined in Y
void f(int i) { a = i; } // ::a
Y* p; // Y<T>
};
Y<A> ya;
The members A::B
, A::a
, and A::Y
of the template argument A
do not affect the binding of names in Y<A>
. ]
[テンプレート化された派生クラスで、メンバー関数内で "this->"を使ってベースクラスメンバー名を修飾する必要があるのはなぜですか?](http://stackoverflow.com/questions/7908248/in-a-テンプレートベースの派生クラス - なぜ必要なのか - ベースクラスのメンバ名-w) – curiousguy