c++ - 模板 C++ 中的迭代器

Question

我正在尝试理解模板。我正在尝试浏览元素，但我不知道如何获取类型 T 的迭代器。

template <typename T, typename _Comparator = less<typename T::value_type>>
class MyClass{
  public:
///...
   typename T <typename T::value_type>::iterator i; // not working
///...
}


int main(){
  MyClass <list<string>> a1;
  MyClass <list<string>, CStrComparator> a2 ( list<string>{ "Hello", "world", "test", "this", "foo", "TEsT", "this", "done" }, CStrComparator ( false ) ); 
}

错误:

/home/michal/Desktop/prog/stl2/main.cpp||In member function ‘std::set<int> MyClass<_Type, _Comparator>::Search(const T&) const’:|
/home/michal/Desktop/prog/stl2/main.cpp|27|error: expected nested-name-specifier before ‘T’|
/home/michal/Desktop/prog/stl2/main.cpp|27|error: expected ‘(’ before ‘T’|
/home/michal/Desktop/prog/stl2/main.cpp|27|error: expected ‘;’ before ‘T’|
/home/michal/Desktop/prog/stl2/main.cpp||In function ‘int main()’:|
/home/michal/Desktop/prog/stl2/main.cpp|179|error: template argument 1 is invalid|
/home/michal/Desktop/prog/stl2/main.cpp|179|error: template argument 2 is invalid|
/home/michal/Desktop/prog/stl2/main.cpp|180|error: ‘t6’ was not declared in this scope|
/home/michal/Desktop/prog/stl2/main.cpp||In constructor ‘MyClass<std::basic_string<char>, _Comparator>::MyClass(const string&, const _Comparator&) [with _Comparator = std::less<char>, std::string = std::basic_string<char>]’:|
/home/michal/Desktop/prog/stl2/main.cpp:118|34|instantiated from here|
/home/michal/Desktop/prog/stl2/main.cpp|75|warning: ‘MyClass<std::basic_string<char> >::sequence’ will be initialized after [-Wreorder]|
/home/michal/Desktop/prog/stl2/main.cpp|74|warning:   ‘std::less<char> MyClass<std::basic_string<char> >::cmp’ [-Wreorder]|
/home/michal/Desktop/prog/stl2/main.cpp|40|warning:   when initialized here [-Wreorder]|
||=== Build finished: 6 errors, 3 warnings ===|

Answer 1

您已经使用了“容器 T 的元素类型”

typename T::value_type

迭代器也是如此:

typename T::iterator i;