对于成员和成员函数的指针，最好的用法是什么？ [英] What's the best use you've had with pointer to members and member functions?

问题描述

指向成员的指针不是很多，但是它们真的很强大，你是如何使用它们的，以及你做过的最酷的事情是什么？

Pointer to members are not used very much but they are really powerful, how have you used them and what's the coolest things you've done?

编辑：
这不是列出可能的东西，例如列出boost :: bind 和 boost :: function aren' t好。相反可能是一个很酷的用法与他们？我知道他们自己很酷，但这不是这个。

This is not so much to list things that are possible, for example listing boost::bind and boost::function aren't good. Instead maybe a cool usage with them? I know they're very cool in themselves but that's not what this is about.

推荐答案

我曾经需要操作标准数据作为纯结构，以便能够存储队列中的所有条件的列表。我不得不绑定结构与GUI和其他过滤器元素等。所以我想出了解决方案，其中使用成员的指针以及成员函数的指针。

I once was needed to operate with criteria data as pure structure to be able to store the list of all criteria in the queue. And I had to bind the structure with the GUI and other filter elements, etc. So I came up with the solution where pointers to members are used as well as pointers to member functions.

假设您有

struct Criteria
{
    typedef std::string Criteria::* DataRefType;
    std::string firstname;
    std::string lastname;
    std::string website;
};

比你可以包裹条件字段，并用

Than you can wrap criteria field and bind with the string representation of the field with

class Field
{
public:
    Field( const std::string& name,
           Criteria::DataRefType ref ):
        name_( name ),
        ref_( ref )
    {}
    std::string getData( const Criteria& criteria )
    {
        return criteria.*ref_;
    }
    std::string name_;
private:
    Criteria::DataRefType ref_;
};

然后您可以注册所有字段，以便随时使用：GUI，序列化， ，等等。

Then you can register all the fields to use whenever you want: GUI, serialization, comparison by field names, etc.

class Fields
{
public:
    Fields()
    {
        fields_.push_back( Field( "First Name", &Criteria::firstname ) );
        fields_.push_back( Field( "Last Name", &Criteria::lastname ) );
        fields_.push_back( Field( "Website", &Criteria::website ) );
    }
    template < typename TFunction >
    void forEach( TFunction function )
    {
        std::for_each( fields_.begin(), fields_.end(),
                       function );
    }
private:
    std::vector< Field > fields_;
};

通过调用 fields.forEach（serialization）; 或

GuiWindow( Criteria& criteria ):
    criteria_( criteria )
{
    fields_.forEach( std::bind1st( 
                         std::mem_fun( &GuiWindow::bindWithGui ),
                         this ) );
}
void bindWithGui( Field field )
{
    std::cout << "name " << field.name_
              << " value " << field.getData( criteria_ ) << std::endl;
};

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