c – 为什么不能使用initializer_list来初始化unique_ptr的向量？

[weixin_38089340]

参见英文答案 > initializer_list and move semantics                                    6个我想知道为什么initializer_list不能与unique_ptr一起使用： std::vector<std::unique_ptr<int>> vptr = {std::make_unique<int>(1), std::make_unique<int>(2)}; 不编译. 然而： std::vector<std::unique_ptr<int>> vptr(2); vptr[0] =std::make_unique<int>(1); vptr[1] =std::make_unique<int>(2); 编译. 和 std::vector<int*>vint={new int{1},new int{2}}; 要么 std::vector<std::shared_ptr<int>> vptr= {std::make_shared<int>(1), std::make_shared<int>(2)}; 编译. unique_ptr变体在clang中给出了此错误消息： In file included from main.cpp:2: In file included from /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/vector:62: /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_construct.h:75:38: error: call to deleted constructor of 'std::unique_ptr<int, std::default_delete<int> >' { ::new(static_cast<void*>(__p)) _T1(std::forward<_Args>(__args)...); } ^ ~~~~~~~~~~~~~~~~~~~~~~~~~~~ /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_uninitialized.h:75:8: note: in instantiation of function template specialization 'std::_Construct<std::unique_ptr<int, std::default_delete<int> >, const std::unique_ptr<int, std::default_delete<int> > &>' requested here std::_Construct(std::__addressof(*__cur), *__first); ^ /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_uninitialized.h:125:2: note: in instantiation of function template specialization 'std::__uninitialized_copy<false>::__uninit_copy<const std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > *>' requested here __uninit_copy(__first, __last, __result); ^ /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_uninitialized.h:278:19: note: in instantiation of function template specialization 'std::uninitialized_copy<const std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > *>' requested here { return std::uninitialized_copy(__first, __last, __result); } ^ /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_vector.h:1284:11: note: in instantiation of function template specialization 'std::__uninitialized_copy_a<const std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > *, std::unique_ptr<int, std::default_delete<int> > >' requested here std::__uninitialized_copy_a(__first, __last, ^ /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/stl_vector.h:377:2: note: in instantiation of function template specialization 'std::vector<std::unique_ptr<int, std::default_delete<int> >, std::allocator<std::unique_ptr<int, std::default_delete<int> > > >::_M_range_initialize<const std::unique_ptr<int, std::default_delete<int> > *>' requested here _M_range_initialize(__l.begin(), __l.end(), ^ main.cpp:10:42: note: in instantiation of member function 'std::vector<std::unique_ptr<int, std::default_delete<int> >, std::allocator<std::unique_ptr<int, std::default_delete<int> > > >::vector' requested here std::vector<std::unique_ptr<int>> vptr = {std::make_unique<int>(1), std::make_unique<int>(2)}; ^ /usr/local/bin/../lib/gcc/x86_64-unknown-linux-gnu/4.9.0/../../../../include/c++/4.9.0/bits/unique_ptr.h:356:7: note: 'unique_ptr' has been explicitly marked deleted here unique_ptr(const unique_ptr&) = delete; ^ 1 error generated.

[weixin_38107144]

向量< T>的构造函数.采用initializer_list< T>将元素从初始化列表复制到向量中.当您处理不可复制的类型时,这不起作用：unique_ptr< T>的设计.防止制作副本.它允许移动,这就是赋值工作的原因：make_unique返回一个rvalue,编译器知道它可以安全移动. 你需要某种构造函数采用initializer_list< T&&>,但C没有这样的构造函数(事实上,正如dyp指出的那样,类型initializer_list< T&&>>甚至功能).