c++ - C++: テンプレート化された基本クラスから関数をオーバーライドする

Question

シンプルバージョンはこちら。以下では、実際の使用例について詳しく説明します。

私は2つのクラスを持っています:

template<class T>
class Base {
protected:
    virtual void foo();
    std::map<std::string*, T*> things;
};

class Derived : public Base<int> {
protected:
    void foo();
};

template<class T>
void Base<T>::foo() {
    for (auto itr = things.begin(); itr < things.end(); ++itr) {
    }
}

void Derived::foo() {
    for (auto itr = things.begin(); itr < things.end(); ++itr) {
    }
}

Derivedの実装でfor ループ条件に問題が発生しましたfoo:

example.cpp: In member function ‘virtual void Derived::foo()’:
example.cpp:23:53: error: no match for ‘operator<’ in ‘itr < ((Derived*)this)->Derived::<anonymous>.Base<int>::things.std::map<_Key, _Tp, _Compare, _Alloc>::end<std::basic_string<char>*, int*, std::less<std::basic_string<char>*>, std::allocator<std::pair<std::basic_string<char>* const, int*> > >()’
example.cpp:23:53: note: candidates are:
In file included from /usr/include/c++/4.7/string:54:0,
                 from example.cpp:2:
/usr/include/c++/4.7/bits/basic_string.h:2590:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const _CharT*, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.7/bits/basic_string.h:2590:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   mismatched types ‘const _CharT*’ and ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’
In file included from /usr/include/c++/4.7/string:54:0,
                 from example.cpp:2:
/usr/include/c++/4.7/bits/basic_string.h:2578:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const _CharT*)
/usr/include/c++/4.7/bits/basic_string.h:2578:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::basic_string<_CharT, _Traits, _Alloc>’
In file included from /usr/include/c++/4.7/string:54:0,
                 from example.cpp:2:
/usr/include/c++/4.7/bits/basic_string.h:2566:5: note: template<class _CharT, class _Traits, class _Alloc> bool std::operator<(const std::basic_string<_CharT, _Traits, _Alloc>&, const std::basic_string<_CharT, _Traits, _Alloc>&)
/usr/include/c++/4.7/bits/basic_string.h:2566:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::basic_string<_CharT, _Traits, _Alloc>’
In file included from /usr/include/c++/4.7/map:62:0,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_multimap.h:822:5: note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const std::multimap<_Key, _Tp, _Compare, _Alloc>&, const std::multimap<_Key, _Tp, _Compare, _Alloc>&)
/usr/include/c++/4.7/bits/stl_multimap.h:822:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::multimap<_Key, _Tp, _Compare, _Alloc>’
In file included from /usr/include/c++/4.7/map:61:0,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_map.h:906:5: note: template<class _Key, class _Tp, class _Compare, class _Alloc> bool std::operator<(const std::map<_Key, _Tp, _Compare, _Alloc>&, const std::map<_Key, _Tp, _Compare, _Alloc>&)
/usr/include/c++/4.7/bits/stl_map.h:906:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::map<_Key, _Tp, _Compare, _Alloc>’
In file included from /usr/include/c++/4.7/map:60:0,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_tree.h:873:5: note: template<class _Key, class _Val, class _KeyOfValue, class _Compare, class _Alloc> bool std::operator<(const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&, const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>&)
/usr/include/c++/4.7/bits/stl_tree.h:873:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:1063:5: note: template<class _Iterator> bool std::operator<(const std::move_iterator<_Iterator>&, const std::move_iterator<_Iterator>&)
/usr/include/c++/4.7/bits/stl_iterator.h:1063:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::move_iterator<_Iterator>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:1057:5: note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::move_iterator<_Iterator>&, const std::move_iterator<_IteratorR>&)
/usr/include/c++/4.7/bits/stl_iterator.h:1057:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::move_iterator<_Iterator>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:349:5: note: template<class _IteratorL, class _IteratorR> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_IteratorR>&)
/usr/include/c++/4.7/bits/stl_iterator.h:349:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::reverse_iterator<_Iterator>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:299:5: note: template<class _Iterator> bool std::operator<(const std::reverse_iterator<_Iterator>&, const std::reverse_iterator<_Iterator>&)
/usr/include/c++/4.7/bits/stl_iterator.h:299:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::reverse_iterator<_Iterator>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:65:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_pair.h:212:5: note: template<class _T1, class _T2> constexpr bool std::operator<(const std::pair<_T1, _T2>&, const std::pair<_T1, _T2>&)
/usr/include/c++/4.7/bits/stl_pair.h:212:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const std::pair<_T1, _T2>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:838:5: note: template<class _Iterator, class _Container> bool __gnu_cxx::operator<(const __gnu_cxx::__normal_iterator<_Iterator, _Container>&, const __gnu_cxx::__normal_iterator<_Iterator, _Container>&)
/usr/include/c++/4.7/bits/stl_iterator.h:838:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const __gnu_cxx::__normal_iterator<_Iterator, _Container>’
In file included from /usr/include/c++/4.7/bits/stl_algobase.h:68:0,
                 from /usr/include/c++/4.7/bits/stl_tree.h:63,
                 from /usr/include/c++/4.7/map:60,
                 from example.cpp:1:
/usr/include/c++/4.7/bits/stl_iterator.h:832:5: note: template<class _IteratorL, class _IteratorR, class _Container> bool __gnu_cxx::operator<(const __gnu_cxx::__normal_iterator<_IteratorL, _Container>&, const __gnu_cxx::__normal_iterator<_IteratorR, _Container>&)
/usr/include/c++/4.7/bits/stl_iterator.h:832:5: note:   template argument deduction/substitution failed:
example.cpp:23:53: note:   ‘std::_Rb_tree_iterator<std::pair<std::basic_string<char>* const, int*> >’ is not derived from ‘const __gnu_cxx::__normal_iterator<_IteratorL, _Container>’

これが機能しないのはなぜですか? 修正するにはどうすればよいですか?

PS: これがテンプレートの特殊化を使用する絶好の機会であることはわかっていますが、それは私のユースケースには適していないと思います。

これが完全な話です。

いくつかのタイプのノードでシーングラフを作成しています。この問題で重要なものは次のとおりです。

シーンの親
シーン地域
シーングループ
SceneComponent

それぞれ次の役割を果たします。

SceneParentテンプレート型 T の一連の子を含みます。
SceneRegionextends SceneParent、 T を次のように指定SceneParent
SceneGroupextends SceneParent、 T を次のように指定SceneComponent

私が実装しようとしている機能はgetVisibleChildren. ビューポートを指定して、SceneComponentレンダリングする必要がある s のセットを受け取りたいです。

SceneParent■ 実装は、すべての子に対して再帰的に呼び出されます。

template< class T >
void SceneParent< T >::getVisibleChildren(const util::Camera& camera,
 std::vector< SceneComponent* >& visibleChildren) const {
    if (!this->isVisible(camera)) {
        return;
    }

    // Get ids into a flat container so the next loop can be parallelized.
    std::vector< std::string* > childIds;
    for (auto itr = this->children.cbegin(); itr < this->children.cend();
     ++itr) {
        childIds.push_back(itr->first);
    }

    // TODO: parallelize this.
    for (auto itr = childIds.cbegin(); itr < childIds.cend(); ++itr) {
        this->children[*itr]->getVisibleChildren(camera, visibleChildren);
    }
}

SceneGroups の実装により、そのすべてのがアキュムレータに追加されますSceneComponent(グループが表示されている場合、そのコンポーネントも表示されていると仮定されます)。したがって、SceneGroupノードは再帰の基本ケースとして機能します。

void SceneGroup::getVisibleChildren(const util::Camera& camera,
 std::vector< SceneComponent* >& visibleChildren) const {
    if (!this->isVisible(camera)) {
        return;
    }

    // If this group is visible, assume all of its components are as well.
    for (auto itr = this->children.cbegin(); itr < this->children.cend();
     ++itr) {
        visibleChildren.push_back(itr->second);
    }
}

私の投稿でここまでたどり着いたあなたは、私の実世界のアプリケーションに (少なくとも穏やかに) 興味を持っていると思います。それは、それが引き起こしているコンパイラエラーだけではありません。ですから、気が向いたら、シーングラフの実装を改善する方法や、このプロジェクトに取り組んでいるときに気をつけなければならないことについてアドバイスをください。

c++ - C++: テンプレート化された基本クラスから関数をオーバーライドする

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