从地图访问对象会导致新对象C 的实例化
Accessing object from map causes instantiation of new object C++
我有一个大类(称其为集合(和一个小类(项目(。
在收集对象的初始化时,它会为小对象创建地图向量。整体结构看起来像:
vector<map<int,Item>> storage;
特别是:
vector<map<int,Node>> layers;
因此,当我调用收集方法以访问项目时,即
layers[vector_index][map_index].some_method();
它迫使项目重新初始化。这是特定代码:
void NN::set_hidden_weights(int hidden_layer_num,int node_index,map<int,double> new_weights){
layers[hidden_layer_num][node_index].set_weights(new_weights); //updates weights
}
我的意思是我从编译器那里得到以下错误:
g++ -o tests.exe tests.cpp ../src/neural_network.cpp -std=c++11
In file included from /usr/include/c++/4.8/bits/stl_map.h:63:0,
from /usr/include/c++/4.8/map:61,
from ../src/neural_network.cpp:8:
/usr/include/c++/4.8/tuple: In instantiation of ‘std::pair<_T1, _T2>::pair(std::tuple<_Args1 ...>&, std::tuple<_Args2 ...>&, std::_Index_tuple<_Indexes1 ...>, std::_Index_tuple<_Indexes2 ...>) [with _Args1 = {const int&}; long unsigned int ..._Indexes1 = {0ul}; _Args2 = {}; long unsigned int ..._Indexes2 = {}; _T1 = const int; _T2 = Node]’:
/usr/include/c++/4.8/tuple:1079:63: required from ‘std::pair<_T1, _T2>::pair(std::piecewise_construct_t, std::tuple<_Args1 ...>, std::tuple<_Args2 ...>) [with _Args1 = {const int&}; _Args2 = {}; _T1 = const int; _T2 = Node]’
/usr/include/c++/4.8/bits/stl_tree.h:140:49: required from ‘std::_Rb_tree_node<_Val>::_Rb_tree_node(_Args&& ...) [with _Args = {const std::piecewise_construct_t&, std::tuple<const int&>, std::tuple<>}; _Val = std::pair<const int, Node>]’
/usr/include/c++/4.8/ext/new_allocator.h:120:4: required from ‘void __gnu_cxx::new_allocator<_Tp>::construct(_Up*, _Args&& ...) [with _Up = std::_Rb_tree_node<std::pair<const int, Node> >; _Args = {const std::piecewise_construct_t&, std::tuple<const int&>, std::tuple<>}; _Tp = std::_Rb_tree_node<std::pair<const int, Node> >]’
/usr/include/c++/4.8/bits/alloc_traits.h:254:4: required from ‘static typename std::enable_if<std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::value, void>::type std::allocator_traits<_Alloc>::_S_construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::_Rb_tree_node<std::pair<const int, Node> >; _Args = {const std::piecewise_construct_t&, std::tuple<const int&>, std::tuple<>}; _Alloc = std::allocator<std::_Rb_tree_node<std::pair<const int, Node> > >; typename std::enable_if<std::allocator_traits<_Alloc>::__construct_helper<_Tp, _Args>::value, void>::type = void]’
/usr/include/c++/4.8/bits/alloc_traits.h:393:57: required from ‘static decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) std::allocator_traits<_Alloc>::construct(_Alloc&, _Tp*, _Args&& ...) [with _Tp = std::_Rb_tree_node<std::pair<const int, Node> >; _Args = {const std::piecewise_construct_t&, std::tuple<const int&>, std::tuple<>}; _Alloc = std::allocator<std::_Rb_tree_node<std::pair<const int, Node> > >; decltype (_S_construct(__a, __p, (forward<_Args>)(std::allocator_traits::construct::__args)...)) = <type error>]’
/usr/include/c++/4.8/bits/stl_tree.h:408:36: required from ‘std::_Rb_tree_node<_Val>* std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_create_node(_Args&& ...) [with _Args = {const std::piecewise_construct_t&, std::tuple<const int&>, std::tuple<>}; _Key = int; _Val = std::pair<const int, Node>; _KeyOfValue = std::_Select1st<std::pair<const int, Node> >; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, Node> >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_Link_type = std::_Rb_tree_node<std::pair<const int, Node> >*]’
/usr/include/c++/4.8/bits/stl_tree.h:1669:64: required from ‘std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::_M_emplace_hint_unique(std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::const_iterator, _Args&& ...) [with _Args = {const std::piecewise_construct_t&, std::tuple<const int&>, std::tuple<>}; _Key = int; _Val = std::pair<const int, Node>; _KeyOfValue = std::_Select1st<std::pair<const int, Node> >; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, Node> >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::iterator = std::_Rb_tree_iterator<std::pair<const int, Node> >; std::_Rb_tree<_Key, _Val, _KeyOfValue, _Compare, _Alloc>::const_iterator = std::_Rb_tree_const_iterator<std::pair<const int, Node> >]’
/usr/include/c++/4.8/bits/stl_map.h:465:8: required from ‘std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type& std::map<_Key, _Tp, _Compare, _Alloc>::operator[](const key_type&) [with _Key = int; _Tp = Node; _Compare = std::less<int>; _Alloc = std::allocator<std::pair<const int, Node> >; std::map<_Key, _Tp, _Compare, _Alloc>::mapped_type = Node; std::map<_Key, _Tp, _Compare, _Alloc>::key_type = int]’
../src/neural_network.cpp:135:27: required from here
/usr/include/c++/4.8/tuple:1090:70: error: no matching function for call to ‘Node::Node()’
second(std::forward<_Args2>(std::get<_Indexes2>(__tuple2))...)
^
/usr/include/c++/4.8/tuple:1090:70: note: candidates are:
../src/neural_network.cpp:12:1: note: Node::Node(int, std::vector<int>)
Node::Node(int node_index, vector<int> input_indices){
^
../src/neural_network.cpp:12:1: note: candidate expects 2 arguments, 0 provided
In file included from ../src/neural_network.cpp:9:0:
../src/neural_network.hpp:12:7: note: Node::Node(const Node&)
class Node{
^
../src/neural_network.hpp:12:7: note: candidate expects 1 argument, 0 provided
../src/neural_network.hpp:12:7: note: Node::Node(Node&&)
../src/neural_network.hpp:12:7: note: candidate expects 1 argument, 0 provided
我没有项目类别的默认构造函数,也没有复制构造函数,无论如何我真正想做的就是操纵项目本身,而不是它的副本。有人对如何进行有任何建议吗?我真的很困惑,为什么当对象项目已经创建时,我会遇到这些初始化错误。
在映射layers[hidden_layer_num][node_index]
上索引运算符的调用会导致用node_index
作为密钥和默认构造值构造新的映射(如果还没有(。您应该使用map::find()
访问已经存在的项目。
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