不完整类型的无效使用/错误的前向声明。可能滥用抽象类？ (C++)
现在我收到错误：
error: ‘oset<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::Comparator’ is an inaccessible base of ‘CaseSensitive’
我花了几个小时试图解决这个问题，但无济于事，希望你们中的一个人可以帮助我。相关代码如下：
template <class T>
class oset;
template <class T>
class oset {
....
public:
class Comparator {
public:
virtual ~Comparator() {}
virtual int compare(T, T) = 0;
};
private:
Comparator *comp;
....
public:
// new empty set:
oset(Comparator*);
....
};
....
class CaseSensitive : oset<string>::Comparator
{
public:
virtual ~CaseSensitive(){}
virtual int compare(string str1, string str2)
{
return strcmp(str1.c_str(), str2.c_str());
}
};
....
int main() {
oset<string>::Comparator *cs = new class CaseSensative();
//error in line above
....
}
我想做的是创建一个抽象 Comparator 对象，以便我可以定义自定义类型顺序来对 oset 进行排序。
谢谢！
now i get the error:
error: ‘oset<std::basic_string<char, std::char_traits<char>, std::allocator<char> > >::Comparator’ is an inaccessible base of ‘CaseSensitive’
I've been trying to figure out the issue for several hours to no avail, hopefully one of you guys can help me. relevant code is below:
template <class T>
class oset;
template <class T>
class oset {
....
public:
class Comparator {
public:
virtual ~Comparator() {}
virtual int compare(T, T) = 0;
};
private:
Comparator *comp;
....
public:
// new empty set:
oset(Comparator*);
....
};
....
class CaseSensitive : oset<string>::Comparator
{
public:
virtual ~CaseSensitive(){}
virtual int compare(string str1, string str2)
{
return strcmp(str1.c_str(), str2.c_str());
}
};
....
int main() {
oset<string>::Comparator *cs = new class CaseSensative();
//error in line above
....
}
What I am trying to do is make an abstract Comparator object so that I can define custom typological orders to sort oset with.
Thanks!
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评论（3）
您从
Comparator私有继承，因此继承关系在类的成员和友元之外不可用。特别是，这会阻止从CaseSensitive*到Comparator*的转换。您可能希望公开继承：除非您另外指定，否则
class的成员和基类都是private；struct的那些是public。You are inheriting privately from
Comparator, so that the inheritance relationship is not available outside members and friends of the class. In particular, that prevents conversion fromCaseSensitive*toComparator*. You probably want to inherit publicly:Unless you specify otherwise, members and base classes of a
classareprivate; and those of astructarepublic.它应该是 new CaseSensative()（顺便说一句，拼写为“sensitive”），并且该类的完整定义必须可用（您很可能没有包含定义它的标头）。
好吧，或者您定义了一个类并尝试使用不存在的类，在这种情况下它应该是
new IgnoreCase()。It should be
new CaseSensative()(which is spelled 'sensitive', BTW), and the full definition of that class must be available (you most likely didn't include a header which defines it).Well, or you defined one class and try to use non-existing one, in which case it should be
new IgnoreCase().您应该在问题中包含 CaseSensative。除非那是问题所在。
You should include CaseSensative in your question. Unless that's the problem.