[英]Undefined Reference to a template Const & function
Function header:(Templated Outer Class Map has inner class Iterator) 函数头:(模板化的外部类映射具有内部类迭代器)
Iterator insert(const std::pair<const T1, T2>&);
Function Implementation: 功能实施:
template<typename T1, typename T2>
typename Map<T1,T2>::Iterator insert(const std::pair<const T1, T2> &p)
Code to call insert function: 调用插入函数的代码:
std::pair<int,char>p = std::make_pair(5, 'z');
mymap3.insert(p);
Compilation with g++ -g -std=c++11, Error: 使用g ++ -g -std = c ++ 11进行编译,错误:
In function `main':
testmap.cpp:535: undefined reference to
Map<int, char>::insert(std::pair<int const, char> const&)'
collect2: error: ld returned 1 exit status
Why does the compiler assumer the definition of insert is now (pair const &) instead of my definition of (const pair &) is there a difference? 为什么编译器现在定义insert(对const&)而不是我对(const pair&)的定义是否存在差异? Am I calling this inappropriately?
我不恰当地称呼这个吗? I'm very befuddled.
我很迷惑。 Yes, this is for class, we are re-implementing map.
是的,这是为了上课,我们正在重新实施地图。 So the function definition was a given, I just need to find out how to call it and make it work.
所以函数定义是给定的,我只需要找出如何调用它并使其工作。
This function: 这个功能:
template<typename T1, typename T2>
typename Map<T1,T2>::Iterator insert(const std::pair<const T1, T2> &p)
when declared outside the class definition of Map
, is not a member function - it defines a global insert
. 当在
Map
的类定义之外声明时,它不是成员函数 - 它定义了一个全局insert
。
This is a member of Map<T1, T2>
declared at namespace scope (ie, outside the class definition): 这是在命名空间范围内声明的
Map<T1, T2>
的成员(即,在类定义之外):
template<typename T1, typename T2>
typename Map<T1,T2>::Iterator Map<T1,T2>::insert(const std::pair<const T1, T2> &p)
Note that the member function name has been qualified by the class name, which in this case is Map<T1, T2>
. 请注意,成员函数名称已由类名限定,在本例中为
Map<T1, T2>
。
On a related note, using a trailing return type would let you get rid of some of the nastiness in the return type, since names in a trailing return type are resolved in the scope of the class: 在相关的说明中,使用尾随返回类型可以让你摆脱返回类型中的一些肮脏,因为尾随返回类型中的名称在类的范围内被解析:
template<typename T1, typename T2>
auto Map<T1, T2>::insert(const std::pair<const T1, T2> &p) -> Iterator;
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