Question

This cites for_each as follows:

  template<class InputIterator, class Function>
  Function for_each(InputIterator first, InputIterator last, Function f);

I have a collection std::list<std::string>, and a function void Do(std::string) works fine when given to for_each along with the iterators. But if I supply a function like void Do(std::string&), it does not compile. Is there a way around it? Or should I forget about it as some RVO like magic is going on? 😀

EDIT:

bool PluginLoader::LoadSharedObjects()                              
{                                                                   
    for_each(l_FileNames.begin(), l_FileNames.end(), bind1st(mem_fun(&PluginLoader::LoadSharedObject),this));                                                                      
}   

void PluginLoader::LoadSharedObject(const std::string sFileName)   
{                                                                   
    void* pHandle = dlopen(sFileName.c_str(), i_LibMode);           
    //if(pHandle == NULL)
    //Check dlerror

    //Add handle to list
} 

Code added. I woul like LoadSharedObject function to be of the form void PluginLoader::LoadSharedObject(const std::string& sFileName) if it is possible.

Answer 1

The error is not with for_each but with bind1st and mem_fun. They simply dont’t support what you’re trying to do. They cannot handle functions which take reference parameters. You could write your own functor, use boost::bind or wait until you’re able to use C++0x lambdas.

Example for your own functor:

struct LoadSharedObjFunctor
{
    PluginLoader *pl;
public:
    explicit(PluginLoader *p)
    : pl(p) {}

    void operator()(std::string const& cref) const
    { return pl->LoadSharedObject(cref); }
};

...
std::for_each(...,...,LoadSharedObjFunctor(this));
...

Of course, you don’t have to use std::for_each. A simple for-loop will do as well.