【发布时间】：2013-03-28 18:43:42
【问题描述】：
此问题确定不可复制类型不能与 Boost Variant 一起使用
Tree类
template <class T = int>
class Tree{
private:
class TreeNode{
public:
std::unique_ptr Nodes
Move constructors and move assignment + other public members
private:
TreeNode(const TreeNode &other); (= delete not supported on compiler)
TreeNode& operator=(const TreeNode &rhs); (= delete not supported on compiler)
}; // End Tree Node Class Definition
Tree(const Tree &other); (= delete not supported on compiler)
Tree& operator=(const Tree &rhs); (= delete not supported on compiler)
public:
Move constructors and move assignment + other public members
};
TreeVisitor类
class TreeVisitor : public boost::static_visitor<bool> {
public:
TreeVisitor() {}
bool operator() (BinarySearchTree<std::string>& tree) const {
return searchTree.load(tree);
}
private:
};
TreeVariant
typedef boost::variant<Tree<std::string>, Tree<int>> TreeVariant;
TreeVariant tree;
Tree<std::string> stringTree;
Tree<int> intTree;
申请Visitors如下
tree = intSearchTree;
boost::apply_visitor(TreeVisitor(), tree)
还使用 boost::bind 来获取所需的参数
boost::bind(TreeVisitor(), tree, val, keyIndex);
类型的编译器错误
error C2248: 'Tree<T>::Tree' : cannot access private member declared in class 'Tree<T>' <----- related to private copy constructor in Tree (not TreeNode)
tree = stringTree; <------- error related to assignment
Tree 编译正确并经过测试。如何解决这些编译错误，这些错误似乎与尝试获取 Tree 类的副本有关，而由于 std::unique_ptr，这是不可能的？
SSCCE
<class T = int>
class Tree{
private:
class TreeNode{
public:
TreeNode() {}
~TreeNode() {}
TreeNode(TreeNode &&other) :
key(other.key), index(other.index), left(std::move(other.left)), right(std::move(other.right))
{
key = index = left = right = nullptr;
}
TreeNode &operator=(BTreeNode &&rhs)
{
if(this != &rhs)
{
key = rhs.key; index = rhs.index;
left = std::move(rhs.left); right = std::move(rhs.right);
rhs.key = rhs.index = rhs.left = rhs.right = nullptr;
}
return *this;
}
TreeNode(const T &new_key, const T &new_index) :
key(new_key), index(new_index), left(nullptr), right(nullptr) {}
friend class Tree;
private:
TreeNode(const BinarySearchTreeNode &other);
TreeNode& operator=(const BinarySearchTreeNode &rhs);
std::unique_ptr<TreeNode> left;
std::unique_ptr<TreeNode> right;
}; // End Tree Node Class Definition
std::unique_ptr<TreeNode> root;
BinarySearchTree(const BinarySearchTree &other);
BinarySearchTree& operator=(const BinarySearchTree &rhs);
public:
Tree() : root(nullptr), flag(false), run(true), leftCount(0), rightCount(0) {}
~Tree() {}
Tree(BinarySearchTree &&other) : root(std::move(other.root)) { other.root = nullptr; }
Tree &operator=(BinarySearchTree &&rhs)
{
if(this != &rhs)
{
root = std::move(rhs.root);
rhs.root = nullptr;
}
return *this;
}
};
使用示例：
bool delete_(){
while(!instances.empty()){
// grab first instance
keyIndex = instances.at(0);
// compute end of the tuple to delete
endIndex = keyIndex + sizeToDelete;
// read the first attribute
try{
temp = boost::trim_copy(dataFile->readData(keyIndex, domainSize));
}
catch (std::exception &e){
printw("Error reading from the data file");
}
// delete tuple from data file
if(!dataFile->deleteTuple(keyIndex, endIndex)){
printw("Error attempting to remove tuple");
if (writer_ != nullptr)
writer_ << "Error attempting to remove tuple";
try{
printw("%s");
// close catalog and search file
}
catch (std::exception &e){
e.what();
}
// close data file
dataFile->closeFile();
return false;
}
try{
int val = boost::lexical_cast<int>(temp);
searchTree = intSearchTree;
boost::bind(BinarySearchTreeVisitor(), searchTree, val, keyIndex);
// delete key index from the index file
if (!boost::apply_visitor(BinarySearchTreeVisitor(), searchTree)){
printw("No index present in index file");
try{
printw(" ");
}
catch (std::exception &e){
}
// close data file
dataFile->closeFile();
return false;
}
}
catch(boost::bad_lexical_cast &e){
/*
* Must be a std::string --- wow who knew
*/
searchTree = stringSearchTree;
boost::bind(BinarySearchTreeVisitor(), searchTree, temp, keyIndex);
// delete key index from the index file
if (!boost::apply_visitor(BinarySearchTreeVisitor(), searchTree)){
printw("No index present in index file");
try{
printw(" ");
// close catalog and search file
}
catch (std::exception &e){
e.what();
}
// close data file
dataFile->closeFile();
return false;
}
}
// clean up the index file
boost::bind(BinarySearchTreeVisitor(), searchTree, keyIndex, sizeToDelete);
boost::apply_visitor(BinarySearchTreeVisitor(), searchTree);
instances.erase(instances.begin());
for(int i= 0; i < instances.size(); i++){
instances.assign(i, instances.at(i) -
sizeToDelete);
}
}
}
【问题讨论】：
-
请发布可编译的代码。 （并且仍然演示问题）删除不重要但仍然演示问题的内容。看这里：sscce.org 了解如何让您的问题更容易回答。
-
@Yakk 我的原始帖子尽可能清楚地说明了一个包含十个类和数千行代码的程序的问题。无需您无限滚动，它就可以做到最好。
-
不，不是。您的
TreeVisitor正在谈论BinarySearchTree，这是一种不知从何而来的类型。Tree应该是BinarySearchTree吗？几乎你所有的delete_函数都与问题无关，你怎么能得到它？TreeNode的成员是否与问题有关？我对此表示怀疑。一个简短的、自包含的编译示例的全部意义在于，您实际上编写了编译并演示问题的代码，并且在仍然演示问题的同时，您可以从中删除所有可以消除的内容。你可以做得更好。 -
并且说“将构造函数移到这里”是没有帮助的。如果它们不重要，请忽略它们。如果它们很重要，请包括它们，并尽可能多地从它们中删除，直到它们只包含重要的部分。然后重复。
-
@Yakk 将
BinarySearchTree更正为Tree并发布了 SSCCE。我试图提供的不是 SSCCE，而是我正在编写的一个非常大的程序的可理解的细分。很抱歉你的例外，并真诚地向你道歉！
标签： c++ c++11 unique-ptr boost-variant