[英]Why does std::vector::iterator::operator-> only drill down one level?
This code fails to compile:此代码无法编译:
void foo(vector<unique_ptr<pair<int, int>>> bar)
{
bar.begin()->first;
}
What's the problem here?这里有什么问题? Shouldn't operator->
drill down until pair
?不应该operator->
向下钻取直到pair
吗?
Shouldn't
operator->
drill down untilpair
?不应该operator->
向下钻取直到pair
吗?
The recursion of operator ->
only works until you get a pointer type. operator ->
的递归仅在您获得指针类型之前有效。 Once that happens the recursion stops and you access what that pointer points to.一旦发生这种情况,递归就会停止,您可以访问该指针指向的内容。 In this case std::vector::iterator::operator->
returns a unique_ptr<pair<int, int>>*
as that pointer type of the element in the vector.在这种情况下, std::vector::iterator::operator->
返回一个unique_ptr<pair<int, int>>*
作为向量中元素的指针类型。 Once you hit that pointer, you are left accessing the members of the unique_ptr
, not the pair<int, int>
it points to.一旦你点击了那个指针,你就只能访问unique_ptr
的成员,而不是它指向的pair<int, int>
。
You can get what you want using你可以得到你想要的使用
(*bar.begin())->first;
so now you are using operator->
of unique_ptr<pair<int, int>>
.所以现在您使用的是operator->
of unique_ptr<pair<int, int>>
。
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