如何将类成员函数传递给第三方库中的方法？ [英] How to pass class member functions to a method in a 3rd party library?

问题描述

以下是我想在第三方库中使用的类的构造函数（因此，不能修改此函数）

The following is the constructor of a class I would like to use in a 3rd party library (so altering this function isn't an option).

template <class Space>
moveset<Space>::moveset(particle<Space> (*pfInit)(rng*),
          void (*pfNewMoves)(long, particle<Space> &,rng*),
          int (*pfNewMCMC)(long,particle<Space> &,rng*))

<然而，不是简单地定义3个全局函数，我需要每个函数知道各种额外的信息，显然我不能通过，因为没有输入参数。为了进一步复杂的问题，我想要使这个moveet对象的几个不同的实例，每个想使用相同的功能，但在不同的底层数据。

However, rather than simply defining 3 global functions, I need each of the functions to know various extra information, which obviously I can't pass as there are no input arguments. To further complicate the issue, I am going to want to make several different instances of this moveset object, each wanting to use the same functions, but upon different underlying data.

我的想法是创建一个持有类沿着这些行，

My thought is to create a holding class something along these lines,

Class DataPlusFunctions {

 public:

   DataPlusFunctions(Data* dataPtr) { dataPtr_ = dataPtr ;}

   smc::particle<cv_state> fInitialise(smc::rng *pRng)
    {

      // the actual function will be a lot more complicated than this and
      // likely to require calling other methods / classes.
      // The Data stored in a different class will be changing...which is
      // important in relation to the pfNewMoves function.

      double value = dataPtr_->value() ;
      return smc::particle<cv_state>(value,likelihood(0,value));          

    }

    ... same for other required functions
 private:

  Data* dataPtr_ ;
}

*

Class MainClass {

...
void IK_PFController::initialise() 
{

   std::vector<DataPlusFunctions> dpfV ;

   for (int i = 0 ; i < NSAMPLERS ; i++)
        dpfV.push_back(DataPlusFunctions(&data[i])) ;


  pSamplers_ = (smc::sampler<cv_state>**)(new void* [NSAMPLERS]) ;

  for (int i = 0 ; i < NSAMPLERS ; i++) {

    // Normal way of calling function, having defined global functions e.g.
    //smc::moveset<cv_state> Moveset(fInitialise, fMove, NULL);

    // How to achieve this given my problem ??????????????
    //smc::moveset<cv_state> Moveset(&dpfV[i]::fInitialise, &dpfV[i]::fMove, NULL);

     pSamplers_[i].SetMoveSet(Moveset);

  }

} 

}

b $ b

是允许的吗？

Is is allowed? If not, is it possible to achieve what I am attempting given that I will be able to alter the moveset class?

推荐答案

如果没有，是否可以实现我试图给出的为了调用成员函数（通过指针），你需要一个适当类型的对象。由于第三方函数需要使用vanilla函数指针，因此你不能传递成员函数。

In order to call a member function (via pointer), you need an object of the appropriate type. Since the 3rd party function requires vanilla function pointers, you cannot pass a member function.

你最好做的就是定义三个函数

The best you could do (AFAIK) is to define three functions

particle<Space> Init(rng*);
void NewMoves(long, particle<Space> &,rng*);
int NewMCMC(long,particle<Space> &,rng*);

并设置这些函数访问的全局变量。例如：

and set a global variable that those functions access. e.g.:

DataPlusFunctions* g = NULL;

particle<Space> Init(rng* r)
{
  // g==NULL handling omitted
  return g->fInitialise(r);
}
// similarly for the others

code> g 在调用第三方函数之前。

and set the value of g before calling the 3rd party function.

优点是你有一个对象可以用来存储状态信息并且你可以用另一个（甚至可以使用接口）替换指向的对象，提供动态行为。

The advantage is that you have an object you can use to store state info and also you can replace the pointed-to object with another (maybe even using interface), providing dynamic behavior.

问题是如果你想在并行设置为全局可能会同时更改两个线程 - 在这种情况下，您可以使用互斥锁或锁来保护它。

The problem is if you want to use this in a parallel setting as the global might be changed by two threads simultaneously -- in this case you could protect it with a mutex or lock.

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