boost之bind

news2024/12/16 17:38:55

简介

用于构造函数对象，其定义在文件bind.hpp中

bind

其底层使用通用的模板类bind_t

template<class R, class F, class L> class bind_t
{
public:

    typedef bind_t this_type;

    bind_t(F f, L const & l): f_(f), l_(l) {}

#define BOOST_BIND_RETURN return
#include <boost/bind/bind_template.hpp>
#undef BOOST_BIND_RETURN

};

bind_t类中包含两个成员

private:
    F f_;//函数
    L l_;//参数列表构造的对象

不带参数的绑定

template<class R, class F>
    _bi::bind_t<R, F, _bi::list0>
    BOOST_BIND(F f)
{
    typedef _bi::list0 list_type;
    return _bi::bind_t<R, F, list_type> (f, list_type());
}

带1个参数的绑定

template<class R, class F, class A1>
    _bi::bind_t<R, F, typename _bi::list_av_1<A1>::type>
    BOOST_BIND(F f, A1 a1)
{
    typedef typename _bi::list_av_1<A1>::type list_type;
    return _bi::bind_t<R, F, list_type> (f, list_type(a1));
}

template<class A1> struct list_av_1
{
    typedef typename add_value<A1>::type B1;
    typedef list1<B1> type;
};

template< class A1 > class list1: private storage1< A1 > 
{
	public:
    explicit list1( A1 a1 ): base_type( a1 ) {}
};

即bind_t中的list类型为list1<B1>,add_value<A1>::type类型为_bi::value< T >,其定义为

template<class T> class value
{
public:

    value(T const & t): t_(t) {}

    T & get() { return t_; }
    T const & get() const { return t_; }

    bool operator==(value const & rhs) const
    {
        return t_ == rhs.t_;
    }

private:

    T t_;
};