c++ - 指向成员函数的指针 - C++ std::list 排序

Question

如何将指向成员函数的指针传递给 std::list.sort()？

这可能吗？谢谢

struct Node {
       uint32_t ID;
       char *   Value;
};

class myClass {
          private:
            uint32_t  myValueLength;
          public:
            list<queueNode *> MyQueue;
            bool compare(Node * first, Node * second);
            bool doStuff();
}

bool myClass::compare(Node * first, Node * second) {
    unsigned int ii =0;
    while (ii < myValueLength)
    {
        if (first-> Value[ii] < second-> Value[ii]) 
        {
            return true;
        } else if (first-> Value[ii] > second-> Value[ii])
        {
            return false;
        }

        ++ii;
    }

    return false;
}

bool myClass::doStuff()
{
    list.sort(compare);
}

我想在类中使用一个长度变量，而不是在比较函数中执行 strlen()(值将始终是相同的长度)

编辑:myValueLength 不是我想从比较函数中访问的唯一变量，我只是简化它以使示例更短。

Answer 1

详述grieve's响应，为什么不使用仿函数？例如:

struct Functor
{
  bool operator()( char * a, char * b )
    { return strcmp(a,b) < 0; }
};

那么你可以使用:

Functor f;
myList.sort(f);

您甚至可以通过定义 operator() 将您的类用作 Functor...

class myClass {
  ...
  bool operator()( queueNode * a, queueNode * b )
  { return compare( a, b ); }

  void doStuff() { MyQueue.sort(*this); }
};

---

简单示例代码:

#include <iostream>
#include <list>
using namespace std;

  // Assumes  TYPE t; cout << t;  is valid.
template<class TYPE>
inline ostream & operator<< ( ostream & theOstream,
                              const list<TYPE> & theList )
{
  typename list<TYPE>::const_iterator listIterator = theList.begin();
  for ( int i = 0;   listIterator != theList.end();  listIterator ++, i ++ )
    theOstream << "    [" << i << "]:   \"" << (*listIterator) << "\"" << endl;
  return theOstream;
}

struct Functor
{
  bool operator()( const char * a, const char * b )
    { return strcmp(a,b) < 0; }
};

int
main()
{
  list<char*>  l;

    /* Load up some example test data... */
  char  s[3];
  s[2] = '\0';
  for (   s[0]='c'; s[0]>='a'; s[0]-- )
    for ( s[1]='c'; s[1]>='a'; s[1]--  )
      l.push_back(strdup(s));

    /* Show us that test data... */
  cout << l << endl;

    /* Sort list. */
  Functor f;
  l.sort(f);

    /* Show us what we have now... */
  cout << l << endl;
}