我无法使用map的迭代器调用show函数 . 有没有办法使用迭代器来做到这一点？

#include

#include

#include

using namespace std;

class A

{

int i;

public:

A(int pi):i(pi) { cout<

void show() const { cout<

~A() { cout<

};

int main()

{

map mymap;

A a(9) , b(8) , c(7);

mymap['a'] = a;

mymap['b'] = b;

mymap['c'] = c;

map::iterator it;

for(it = mymap.begin(); it != mymap.end() ; it++)

(*(it->second)).show();

return 0;

}

在使用 it->second.show() 时，我收到以下错误：

在/ usr / include / c /4.9/bits/stl_map.h:63:0中包含的文件中，来自/ usr / include / c /4.9/map:61，来自3：/ usr / include / c /4.9/元组：在实例化'std :: pair <_t1> :: pair(std :: tuple <_args1 ...>＆，std :: tuple <_args2 ...>＆，std :: _ Index_tuple <_indexes1 . ..>，std :: _ Index_tuple <_indexes2 ...>)[with Args1 = {char &&}; long unsigned int ... Indexes1 = {0ul}; Args2 = {}; long unsigned int ... Indexes2 = {}; _T1 = const char; _T2 = A]'：/ usr / include / c /4.9/tuple:1093:63：从'std :: pair <_t1> :: pair(std :: piecewise_construct_t，std :: tuple <_args1 .. .>，std :: tuple <_args2 ...>)[with _Args1 = {char &&}; _Args2 = {}; _T1 = const char; _T2 = A]'/ usr / include / c /4.9/ext/new_allocator.h:120:4：需要'void __gnu_cxx :: new_allocator :: construct(Up *， Args && ...)[with _Up = std :: pair; _Args = {const std :: piecewise_construct_t＆，std :: tuple，std :: tuple <>}; _Tp = std :: _ Rb_tree_node>]'/ usr / include / c /4.9/bits/alloc_traits.h:253:4：需要'static std :: _ Require :: __ construct_helper :: type> std： ：allocator_traits :: _ S_construct(Alloc＆， Tp *， Args && ...)[with _Tp = std :: pair; _Args = {const std :: piecewise_construct_t＆，std :: tuple，std :: tuple <>}; _Alloc = std :: allocator >>; std :: _ Require :: __ construct_helper <_tp> :: type> = void]'/ usr / include / c /4.9/bits/alloc_traits.h:399:57：'static decltype(S_construct( a， p) ，(forward <_args>)(std :: allocator_traits :: construct :: __ args)...))std :: allocator_traits :: construct(Alloc＆， Tp *， Args && ...)[with Tp = std ：：对; Args = {const std :: piecewise_construct_t＆，std :: tuple，std :: tuple <>}; Alloc = std :: allocator >>; decltype(S_construct( a， p，(forward <_args>)(std :: allocator_traits :: construct :: __ args)...))=]'/ usr / include / c /4.9/bits/stl_tree.h:423 ：42：需要'std :: _ Rb_tree_node <_val> * std :: _ Rb_tree <_key> :: _ M_create_node( Args && ...)[with _Args = {const std :: piecewise_construct_t＆，std :: tuple，std :: tuple <>}; _Key = char; _Val = std :: pair; _KeyOfValue = std :: _ Select1st>; _Compare = std :: less; _Alloc = std :: allocator>; std :: _ Rb_tree <_key> :: _ Link_type = std :: _ Rb_tree_node> *]'/ usr / include / c /4.9/bits/stl_tree.h:1790:64：'std要求:: _ Rb_tree <_key> :: iterator std :: _ Rb_tree <_key> :: _ M_emplace_hint_unique(std :: _ Rb_tree <_key> :: const_iterator， Args && ...)[with _Args = {const std :: piecewise_construct_t＆，std :: tuple，std :: tuple <>}; _Key = char; _Val = std :: pair; _KeyOfValue = std :: _ Select1st>; _Compare = std :: less; _Alloc = std :: allocator>; std :: _ Rb_tree <_key> :: iterator = std :: _ Rb_tree_iterator>; std :: _ Rb_tree <_key> :: const_iterator = std :: _ Rb_tree_const_iterator>]'/ usr / include / c /4.9/bits/stl_map.h:519:8：从'std：需要： ：map <_key> :: mapped_type＆std :: map <_key> :: operator [](std :: map <_key> :: key_type &&) [用_Key = char; _Tp = A; _Compare = std :: less; _Alloc = std :: allocator>; std :: map <_key> :: mapped_type = A; std :: map <_key> :: key_type = char] '17：14：从这里需要/ usr / include / c /4.9/tuple:1104:70：错误：没有匹配函数来调用'A :: A()'秒(std :: forward (std :: get ( tuple2))...)^ / usr / include / c /4.9/tuple:1104:70：注意：候选人是：9：5：注意：A :: A(int)9：5：注意：候选人需要1个参数，0提供5：7：注意：constexpr A :: A(const A＆)5：7：注意：候选人期望1个参数，0提供