[英]C++ passing std::unique_ptr as an argument
I tried to implement binary tree using std::unique_ptr
but errors come up and I don't understand the output error. 我尝试使用
std::unique_ptr
实现二叉树,但是出现错误,并且我不理解输出错误。
The code is the following: 代码如下:
#include <iostream>
#include <memory>
#include <functional>
#include <utility>
template <typename T>
class BinTreeNode {
public:
BinTreeNode(T key): data {key}, left {nullptr}, right {nullptr} {}
~BinTreeNode() {}
T data;
std::unique_ptr<BinTreeNode<T>> left;
std::unique_ptr<BinTreeNode<T>> right;
};
template <typename T>
class BinTree {
public:
BinTree() : root {nullptr} {}
~BinTree() {}
std::unique_ptr<BinTreeNode<T>> root;
void insert(std::unique_ptr<BinTreeNode<T>> node, T key);
};
template <typename T>
void BinTree<T>::insert(
std::unique_ptr<BinTreeNode<T>> node,
T key)
{
if(node){ // != nullptr
if(node->data < key) insert(node->right, key);
else insert(node->left, key);
}
else{
std::unique_ptr<BinTreeNode<T>> u_ptr(new BinTreeNode<T>(key));
node = std::move(u_ptr);
}
}
int main(){
BinTree<int> tree();
tree.insert(tree.root, 10);
}
I assume the error is in insert function and is related to argument initialisation. 我认为错误是在插入函数中,并且与参数初始化有关。
BinTree.cpp:65:27: error: use of deleted function 'std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinTreeNode;
BinTree.cpp:65:27:错误:使用删除的函数'std :: unique_ptr <_Tp,_Dp> :: unique_ptr(const std :: unique_ptr <_Tp,_Dp>&)[with _Tp = BinTreeNode; _Dp = std::default_delete >]' tree.insert(tree.root, 10);
_Dp = std :: default_delete>]'tree.insert(tree.root,10); ^
^
In file included from /usr/include/c++/4.9/memory:81:0, from BinTree.cpp:2: /usr/include/c++/4.9/bits/unique_ptr.h:356:7: note: declared here unique_ptr(const unique_ptr&) = delete;
在/usr/include/c++/4.9/memory:81:0中包含的文件中,从BinTree.cpp:2:/usr/include/c++/4.9/bits/unique_ptr.h:356:7:注意:在此处声明unique_ptr (const unique_ptr&)=删除; ^
^
BinTree.cpp:35:6: error: initializing argument 1 of 'void BinTree::insert(std::unique_ptr >, T) [with T = int]' void BinTree::insert( ^
BinTree.cpp:35:6:错误:初始化'void BinTree :: insert(std :: unique_ptr>,T)[with T = int]'的参数1 void BinTree :: insert(^
BinTree.cpp: In instantiation of 'void BinTree::insert(std::unique_ptr >, T) [with T = int]': BinTree.cpp:65:27: required from here BinTree.cpp:40:47: error: use of deleted function 'std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinTreeNode;
BinTree.cpp:在'void BinTree :: insert(std :: unique_ptr>,T)[with T = int]'的实例中:BinTree.cpp:65:27:从此处需要BinTree.cpp:40:47:错误:使用删除的函数'std :: unique_ptr <_Tp,_Dp> :: unique_ptr(const std :: unique_ptr <_Tp,_Dp>&)[with _Tp = BinTreeNode; _Dp = std::default_delete >]'
_Dp = std :: default_delete>]'
if(node->data < key) insert(node->right, key);if(node-> data <键)insert(node->右键,键); ^
^
In file included from /usr/include/c++/4.9/memory:81:0, from BinTree.cpp:2: /usr/include/c++/4.9/bits/unique_ptr.h:356:7: note: declared here unique_ptr(const unique_ptr&) = delete;
在/usr/include/c++/4.9/memory:81:0中包含的文件中,从BinTree.cpp:2:/usr/include/c++/4.9/bits/unique_ptr.h:356:7:注意:在此处声明unique_ptr (const unique_ptr&)=删除; ^
^
BinTree.cpp:35:6: error: initializing argument 1 of 'void BinTree::insert(std::unique_ptr >, T) [with T = int]' void BinTree::insert( ^
BinTree.cpp:35:6:错误:初始化'void BinTree :: insert(std :: unique_ptr>,T)[with T = int]'的参数1 void BinTree :: insert(^
BinTree.cpp:41:30: error: use of deleted function 'std::unique_ptr<_Tp, _Dp>::unique_ptr(const std::unique_ptr<_Tp, _Dp>&) [with _Tp = BinTreeNode;
BinTree.cpp:41:30:错误:使用删除的函数'std :: unique_ptr <_Tp,_Dp> :: unique_ptr(const std :: unique_ptr <_Tp,_Dp>&)[with _Tp = BinTreeNode; _Dp = std::default_delete >]' else insert(node->left, key);
_Dp = std :: default_delete>]'else insert(node-> left,key); ^
^
In file included from /usr/include/c++/4.9/memory:81:0, from BinTree.cpp:2: /usr/include/c++/4.9/bits/unique_ptr.h:356:7: note: declared here unique_ptr(const unique_ptr&) = delete;
在/usr/include/c++/4.9/memory:81:0中包含的文件中,从BinTree.cpp:2:/usr/include/c++/4.9/bits/unique_ptr.h:356:7:注意:在此处声明unique_ptr (const unique_ptr&)=删除; ^
^
BinTree.cpp:35:6: error: initializing argument 1 of 'void BinTree::insert(std::unique_ptr >, T) [with T = int]' void BinTree::insert(
BinTree.cpp:35:6:错误:初始化'void BinTree :: insert(std :: unique_ptr>,T)[with T = int]'的参数1 void BinTree :: insert(
The error is caused by you trying to copy-construct the argument of BinTree::insert
from tree.root
. 该错误是由您尝试从
tree.root
复制构造BinTree::insert
的参数tree.root
。 std::unique_ptr
is move-only. std::unique_ptr
仅可移动。
My guess is that node
in BinTree::insert
should be passed by reference. 我的猜测是
BinTree::insert
中的node
应该通过引用传递。 Reasons: 原因:
std::move
the tree.root
into it (if passed by value), which would steal the ownership std::move
tree.root
std::move
到其中(如果通过值传递),这将窃取所有权 BinTree::insert
, these changes are not made to pass tree.root
BinTree::insert
中BinTree::insert
移动分配,而不会通过tree.root
进行这些更改。
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