我试图将unique_ptr的unordered_map移动到另一个映射中,但在下面得到编译错误。将unique_ptr的unordered_map移动到另一个
#include <memory>
#include <unordered_map>
#include <string>
int main()
{
std::unordered_map<int, std::unique_ptr<int>> aMap;
std::unordered_map<int, std::unique_ptr<int>> bMap;
std::unique_ptr<int> ptr(new int);
*ptr = 10;
aMap.insert(std::make_pair(0, std::move(ptr)));
std::move(aMap.begin(), aMap.end(), bMap.end());
return 0;
}
1>------ Build started: Project: Testing, Configuration: Debug Win32 ------
1>Build started 08.07.2012 23:54:16.
1>InitializeBuildStatus:
1> Creating "Debug\Testing.unsuccessfulbuild" because "AlwaysCreate" was specified.
1>ClCompile:
1> main.cpp
1>d:\progs\visual studio 2010\vc\include\utility(260): error C2166: l-value specifies const object
1> d:\progs\visual studio 2010\vc\include\utility(259) : while compiling class template member function 'std::pair<_Ty1,_Ty2> &std::pair<_Ty1,_Ty2>::operator =(std::pair<_Ty1,_Ty2> &&)'
1> with
1> [
1> _Ty1=const int,
1> _Ty2=std::unique_ptr<int>
1> ]
1> d:\coding\testing\main.cpp(12) : see reference to class template instantiation 'std::pair<_Ty1,_Ty2>' being compiled
1> with
1> [
1> _Ty1=const int,
1> _Ty2=std::unique_ptr<int>
1> ]
1>
1>Build FAILED.
1>
1>Time Elapsed 00:00:00.64
========== Build: 0 succeeded, 1 failed, 0 up-to-date, 0 skipped ==========
我不认为StackOverflow是有史以来最重要的东西,更不用说重新开始 – Fraser 2012-07-08 22:40:13
我想我现在是延迟:) – bitgregor 2012-07-08 22:59:09
我相信部分问题是插入和make_pair的组合正试图调用复制唯一ptr的构造函数,它不存在。如果您将unique_ptr更改为shared_ptr,它将会编译到您的std :: move(aMap.begin()...也就是说,您在make_pair的争论中对std :: move有正确的想法,就好像您一样这是独立的,但它工作,但失败,并尝试调用一个Map.insert上的复制构造函数。 – Trickfire 2012-07-08 23:08:15