c – 如何修复STL样式容器以保存不完整或抽象类型?
发布时间:2020-12-16 09:44:58 所属栏目:百科 来源:网络整理
导读:几天前,我自己尝试用与STL容器相同的样式编写基本树实现.现在我正在尝试在我的代码中使用它,但是有两个东西似乎不能用于说std :: vector.即,使用不完整类型和使用抽象类型. 如何修复我的树实现以获得此功能?我试着简化我的代码,主要向您??展示相关部分. TES
几天前,我自己尝试用与STL容器相同的样式编写基本树实现.现在我正在尝试在我的代码中使用它,但是有两个东西似乎不能用于说std :: vector.即,使用不完整类型和使用抽象类型.
如何修复我的树实现以获得此功能?我试着简化我的代码,主要向您??展示相关部分. TEST.CPP #include "util/tree.hpp" #include <vector> struct IncompleteType; class AbstractType { public: virtual void do_something() = 0; }; class Test { public: Test() = default; private: tree<IncompleteType> incompleteTree; std::vector<IncompleteType> incompleteVector; tree<AbstractType> abstractTree; std::vector<AbstractType> abstractVector; }; struct IncompleteType { int completed; }; util / tree.hpp(浓缩) template <class T,class Alloc = std::allocator<T> > class tree { public: typedef Alloc allocator_type; typedef typename Alloc::value_type value_type; typedef value_type& reference; typedef const value_type& const_reference; typedef typename Alloc::difference_type difference_type; typedef typename Alloc::size_type size_type; class node { public: value_type data; const std::vector<std::unique_ptr<node> >& get_children() const { return children_; } node* get_parent() const { return parent_; } node* get_right() const { return right_; } bool operator== (const node&) const; size_t size() const; bool has_ancestor(const node* n) const { return parent_ != nullptr && (parent_ == n || parent_->has_ancestor(n)); } friend class tree; protected: std::vector<std::unique_ptr<node> > children_; node* parent_ = nullptr; node* right_ = nullptr; node() = default; node(value_type data) : data(data) {} }; class iterator { // ... }; class const_iterator { // ... }; tree() = default; tree(const tree&) = default; tree& operator= (const tree&) = default; // iterators begin(),etc ... // operators ... // size(),empty(),... node* get_root() { return &root_; } const node* get_root() const { return &root_; } node* add_new_node(const value_type& val) { return add_new_node_to(&root_,val); } node* add_new_node_to(node*,const value_type&); bool prune_node(node*&); private: node root_; }; 当使用g -O3 -Wall -Wextra -pedantic -std = c 11 test.cpp进行编译时,我得到以下输出: In file included from test.cpp:1:0: util/tree.hpp: In instantiation of ‘class tree<IncompleteType>::node’: util/tree.hpp:138:7: required from ‘class tree<IncompleteType>’ test.cpp:19:30: required from here util/tree.hpp:28:14: error: ‘tree<T,Alloc>::node::data’ has incomplete type value_type data; ^ test.cpp:6:8: error: forward declaration of ‘tree<IncompleteType>::value_type {aka struct IncompleteType}’ struct IncompleteType; ^ In file included from test.cpp:1:0: util/tree.hpp: In instantiation of ‘class tree<AbstractType>::node’: util/tree.hpp:138:7: required from ‘class tree<AbstractType>’ test.cpp:21:30: required from here util/tree.hpp:47:3: error: cannot allocate an object of abstract type ‘AbstractType’ node(value_type data) : data(data) {} ^ test.cpp:8:7: note: because the following virtual functions are pure within ‘AbstractType’: class AbstractType ^ test.cpp:11:15: note: virtual void AbstractType::do_something() virtual void do_something() = 0; ^ In file included from test.cpp:1:0: util/tree.hpp:28:14: error: cannot declare field ‘tree<AbstractType>::node::data’ to be of abstract type ‘AbstractType’ value_type data; ^ test.cpp:8:7: note: since type ‘AbstractType’ has pure virtual functions class AbstractType ^ 我的树有这些类型的问题,而std :: vector没有.我可以看到它与我在节点中存储数据的方式有关,但是当我试图找到正确的方法时,我正在画一个空白…如果不是类型value_type,我该如何存储? 解决方法
由于类型不完整,编译器无法确定其大小.由于需要通过值存储对象的大小,编译器会对它抱怨.如果必须处理不完整的类型,则需要使用指针容器.例如,在Test中你可以使用std :: vector< std :: unique_ptr< incompleteType>>或std :: vector< IncompleteType *>.
您的代码中还有另一个问题.树和向量失败与AbstractClass,因为您试图按值存储它.由于它具有纯虚函数,因此在创建节点时无法实例化它. (编辑:李大同) 【声明】本站内容均来自网络,其相关言论仅代表作者个人观点,不代表本站立场。若无意侵犯到您的权利,请及时与联系站长删除相关内容! |