我将此代码从Visual C++ 6.0(它也适用于较旧的GCC++)移植到Visual Studio 2010 C++。代码编译但引发异常。基类是否可以提供派生类实现的迭代器接口?
我有一个基类CncMatchedQueryAtom。该类用于包含不同类型的目标原子(这是一个图匹配应用程序)的匹配,对于99%的情况,查询和目标之间存在一对一匹配。这由派生类CncMatchedQueryAtomSimple处理。这个课程效果很好。问题是一些查询原子与原子组匹配,这是由类CncMatchedQueryAtomGroup处理的。这个类包含一个匹配原子的矢量。我希望在基类中定义的迭代器类在派生类中封装矢量迭代器,以便begin()返回vector的begin(),end返回vector的end()。 旧版本在运行时的end()上存在问题,因为它通过以下方式进行转换:
return & * group.end();
Visual C++不再允许这么做 那么基类如何指定派生类可以实现的迭代器呢?这对我来说似乎不是很明显,但我是C++的新手。与我合作过的经验丰富的C++开发人员也不知道。
基本上,我希望基类具有提供派生类实现的开始和结束函数的方法。
下面是代码:
class CncMatchedQueryAtom
{
protected:
int notBlockAllocated;
public:
int allocateIndividually() const
{
return notBlockAllocated;
}
const CncAtom *queryAtom;
CncAtom *queryAtomVolitile() const
{
return (CncAtom*)queryAtom;
}
// set when the class has been allocated by newing
// intialize all default constructors to be notBlockAllocated
CncMatchedQueryAtom()
: notBlockAllocated(1)
, queryAtom(NULL) // i don't think this needs to be initialized to null
{
}
CncMatchedQueryAtom(int noBlock)
: notBlockAllocated(noBlock)
, queryAtom(NULL) // i don't think this needs to be initialized to null
{
}
// may not need this now that it's a virtual!
CncMatchedQueryAtom(const CncMatchedQueryAtom &that)
: queryAtom(NULL)
{
*this = that;
}
// this needs to be virtual so when delete CncMatchedQueryAtom is called
// the virtual calss members are destructed too
virtual ~CncMatchedQueryAtom()
{
}
virtual void dump() const =0;
virtual void clearMapping() =0;
virtual CncMatchedQueryAtom *newCopy() const =0;
virtual void coverHits(class CncTarget *) const = 0;
// iterates over all matched target atoms for this query atom
class iterator
{
private:
CncMatchedTargetAtom *ptr;
public:
iterator()
{
}
iterator(const CncMatchedTargetAtom *targetAtom) // constructor from a target ptr
:ptr((CncMatchedTargetAtom *)targetAtom)
{
}
iterator(const iterator &oldOne)
:ptr(oldOne.ptr)
{
}
~iterator()
{
}
int operator==(const iterator &that) const
{
return ptr==that.ptr;
}
int operator!=(const iterator &that) const
{
return ptr!=that.ptr;
}
const CncMatchedTargetAtom &operator*() const
{
return *ptr;
}
iterator operator++(int NotUsed) // post increment
{
iterator returnValue(*this);
++ptr;
return returnValue;
}
iterator &operator++() // pre increment
{
++ptr;
return *this;
}
int operator<(const iterator &rhs) const
{
return (this->ptr < rhs.ptr);
}
CncMatchedTargetAtom *operator->()
{
return ptr;
}
};
virtual iterator begin() const =0;
virtual iterator end() const =0;
virtual int size() const = 0;
virtual double molecularWeight() const = 0;
const CncAtom *getFirstTargetAtom() const
{
return (*begin()).matchedTargetAtom;
}
CncAtom *getFirstTargetAtomVolitile() const
{
return (CncAtom*)getFirstTargetAtom();
}
}; // class CncMatchedQueryAtom
class CncMatchedQueryAtomSimple : public CncMatchedQueryAtom
{
public:
// we need a constructor here since this is allocated with blockAlloc
CncMatchedQueryAtomSimple()
: CncMatchedQueryAtom(0)
{
}
// we use simple.targetAtom as a temporary variable
// used to pass to matching functions
CncMatchedTargetAtom simple;
void clearIt()
{
queryAtom=NULL;
notBlockAllocated=0;
}
// if queryAtom is an element-type atom (or Lp or A atom)
void dump() const;
void clearMapping()
{
}
CncMatchedQueryAtom *newCopy() const
{
// since this is usually not allocatedIndividually I'll set
// the notBlockAllocatedFlag on the copy to be sure if this
// does happen it will individually deallocate it
CncMatchedQueryAtomSimple *retVal = new CncMatchedQueryAtomSimple(*this);
retVal->notBlockAllocated = 1;
return (CncMatchedQueryAtom *)retVal;
}
void coverHits(class CncTarget *) const;
iterator begin() const
{
return &simple;
}
iterator end() const
{
return &simple+1;
}
int size() const
{
return 1;
}
double molecularWeight() const
{
return CncMolGetAtomicMassAve(simple.matchedTargetAtom->getAtomicNumber());
}
}; // class CncMatchedQueryAtomSimple
class CncMatchedQueryAtomGroup : public CncMatchedQueryAtom
{
public:
// if queryAtom is an R- or X-group searching for
std::vector<CncMatchedTargetAtom> group;
void dump() const;
void clearMapping()
{
group.clear();
}
CncMatchedQueryAtom *newCopy() const
{
return new CncMatchedQueryAtomGroup(*this);
}
void coverHits(class CncTarget *) const;
iterator begin() const
{
return &*group.begin();
}
iterator end() const
{
// this is a hack, works with Visual C++ 6.0 and older GCC++ but not VS C++ 2010
return &*group.end(); // Throws error at runtime! Iterator Not Dereferencable
}
int size() const
{
return group.size();
}
double molecularWeight() const
{
double sum=0;
std::vector<CncMatchedTargetAtom>::const_iterator q;
for (q=group.begin()
; q!=group.end()
; ++q)
{
sum += CncMolGetAtomicMassAve(q->matchedTargetAtom->getAtomicNumber());
}
return sum;
}
}; // class CncMatchedQueryAtom
的迭代器是如何被调用的例子:
// Sample call to the iterator
// (*elem)->getMatchedAtom() returns a CncMatchedQueryAtom *
CncMatchedQueryAtom::iterator atomMatched;
// welp it looks like we have to do these
//(*elem)->getFirstTargetAtom
for (atomMatched=(*elem)->getMatchedAtom()->begin()
; atomMatched!=(*elem)->getMatchedAtom()->end() // Runtime exception here!
; ++atomMatched)
{
existenceFingerprint.setBit(
atomMatched->matchedTargetAtom->indexInStructure);
}
感谢,但愿这不是太多的代码......
为了再强调一下,它是_never_合法代码,并且从未保证在VC6中也能工作。 – ildjarn 2012-02-17 18:47:19
对,指针是一种随机访问迭代器,它是'vector :: iterator'的有效选择。一个指针可以被分配一个指向另一个容器的指针,而不是迭代器合约的一部分。它只是偶然为VC6工作。 – 2012-02-17 18:58:24
这段代码也适用于gcc。我希望如果基类提供一个迭代器“接口”来代理真正的迭代器。这在C++中是不可能的吗?这种打败物体的目的。 – whomer 2012-02-17 19:33:55