find_if在MFC容器中，迭代器派生自std :: iterator

>回到家后，我终于打破了调试器来跟踪这个奇怪的行为（见注释）。After arriving home, I finally broke out the debugger to track that strange behaviour (see comments).令我失望的是，我发现 BaseMFCIter 是由对迭代器的理解非常有限的人设计的 ：复制构造函数和赋值运算符完全错误：它们创建了一个新的 begin 迭代器 - 为同一集合。然而，这意味着迭代器永远不能从函数返回。To my dismay, I found out that the BaseMFCIter was designed by someone with very limited understanding of what an iterator is: the copy constructor and assignment operator were completely wrong: they had the effect of creating a new begin iterator - for the same collection. This however, means that an iterator could never be returned from a function.因此，我修复它（首先通过实现它，然后通过删除现在冗余的构造函数和operator =赞成编译器生成的默认实现）。Therefore, I fixed it (first by implementing it right, later by removing the now-redundant constructor and operator= in favour of the compiler-generated default implementations).git clone git://gist.github.com/1353471.git 分钟前依赖于默认生成的副本构造函数和分配 sehe 12分钟前fixed broken copy constructor and assignment li> > sehe 25小时前（ MFC容器CObList的STL迭代器）sehe 11 minutes ago rely on default generated copy constructor and assignment insteadsehe 12 minutes ago fixed broken copy constructor and assignmentsehe 65 minutes ago tentativeDmitry 73 minutes ago Attempt at find_if with predicatesehe Heeren 25 hours ago Fixed and Tested (VS2010)sehe 25 hours ago ( STL iterator for MFC container CObList ) #include "afxwin.h"#include "afxtempl.h"#include <iostream>#include <algorithm>#include <cstdlib>#include <string>#include <iterator>class myCObject : public CObject{public: myCObject( const std::string& val ) { x = val; } std::string x;};template < typename Item, class Cont, class Key = POSITION >class BaseMFCIter : public std::iterator < std::input_iterator_tag, Item >{public: // Define types for the 2 member functions to be used: typedef Key (Cont::*GetFirstFunctionPtr) () const; typedef Item (Cont::*GetNextFunctionPtr) (Key&) const; // Default constructor, makes a null iterator, equal to BaseMFCIter::end() BaseMFCIter() : m_pCont(0), m_Pos(0), m_GetFirstFunc(0), m_GetNextFunc(0), m_End(true) {} // Constructor taking pointer to container and the iteration functions BaseMFCIter(Cont* pCont, GetFirstFunctionPtr pFF, GetNextFunctionPtr pNF) : m_pCont(pCont), m_Pos(0), m_GetFirstFunc(pFF), m_GetNextFunc(pNF) { init(); } bool operator == (const BaseMFCIter& rhs) const { return (m_Pos == rhs.m_Pos && m_End == rhs.m_End); } bool operator != (const BaseMFCIter& rhs) const { return !operator==(rhs); } BaseMFCIter& operator ++ () { advance(); return *this; } BaseMFCIter& operator ++ (int) { BaseMFCIter ret(*this); advance(); return ret; } Item operator * () { return m_Item; } Item operator -> () { return m_Item; } static BaseMFCIter end () { return BaseMFCIter(); } // end() returns default null iteratorprivate: Item m_Item; // Current item from container Cont* m_pCont; // Pointer to container Key m_Pos; // Key to item in container bool m_End; // Flag to indicate end of container reached // Pointers to container iteration functions GetFirstFunctionPtr m_GetFirstFunc; GetNextFunctionPtr m_GetNextFunc; // Use container GetFirst & GetNext functions to set to first element, or end() if not found void init() { m_Pos = 0; m_End = true; if (m_pCont && m_GetFirstFunc != 0) { m_Pos = (m_pCont->*m_GetFirstFunc)(); advance(); } } // Use container GetNext function to find next element in container void advance() { m_End = m_Pos ? false : true; m_Item = (m_Pos && m_pCont && m_GetNextFunc != 0) ? (m_pCont->*m_GetNextFunc)(m_Pos) : Item(); }};struct Container : public CObList{ myCObject* GetNext(POSITION& rPosition) { return dynamic_cast<myCObject*>(CObList::GetNext(rPosition)); } myCObject const* GetNext(POSITION& rPosition) const { return dynamic_cast<const myCObject*>(CObList::GetNext(rPosition)); }};class ListIter : public BaseMFCIter < const myCObject*, Container, POSITION >{public: ListIter( Container* pObj = 0) : BaseMFCIter< const myCObject*, Container, POSITION > (pObj, &CObList::GetHeadPosition, &Container::GetNext) { }};struct Comparator{ Comparator(const std::string& compareTo) : stringToCompare(compareTo) {} bool operator() ( const myCObject* lhs ) const { return 0 == lhs->x.compare( stringToCompare ); } private: const std::string stringToCompare;};void main( ){ myCObject* m = new myCObject( "one" ); myCObject* n = new myCObject( "two" ); myCObject* p = new myCObject( "three" ); myCObject* q = new myCObject( "four" ); Container cont; cont.AddHead( m ); cont.AddHead( n ); cont.AddHead( p ); cont.AddHead( q ); Comparator pred("three"); ListIter iter = ListIter(&cont), endIter = ListIter( ); ListIter foundIter = std::find_if( iter, endIter, pred ); if (endIter != foundIter) { std::cout << "foundIter x is: " << foundIter->x << std::endl; } else { std::cout << "not found" << std::endl; }} 这篇关于find_if在MFC容器中，迭代器派生自std :: iterator的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持！ 1403页，肝出来的..