ugmisc::member_caller< Access > Struct Template Reference

#include <ugmisc/member.hpp>

Public Member Functions
template<class... T>
constexpr auto	operator() (T &&...objs) const

Static Public Member Functions
template<class F>
static constexpr default_function< F >	fallback (F &&f)
template<class... T>
static constexpr wrapped_objects< void, T... >	with (T &&...objs)

Detailed Description

template<class Access>
struct ugmisc::member_caller< Access >

Calls a named member function of objects, trying them in sequence until one will accept the arguments, optionally providing a fallback default value.

For example:

UGMISC_DECL_MEMBER_ACCESS(Access, foo); // Declares a foo accessor called Access.
auto val = member_caller<Access>::fallback( get_default )(x, y)(1, 2);

val is the value of the first of these expressions which is valid:

1. x.foo(1, 2)
2. std::invoke(x.foo, 1, 2)
3. y.foo(1, 2)
4. std::invoke(y.foo, 1, 2)
5. get_default(1, 2)
6. get_default()

The inclusion of the std::invoke variant of the call allows a tried object to have a poiner-to-member member called foo, and the first argument supplied is then the object whose member will be the callable that takes the rest of the arguments.

Note

In C++17, std::invoke is not constexpr. std::invoke is declared constexpr starting with C++20.

It may be more convenient to use member_caller as an object.

UGMISC_DECL_MEMBER_ACCESS(Access, foo); // Declares a foo accessor called Access.
auto caller = member_caller<Access>{};
auto val = caller.fallback( get_default )(x, y)(1, 2);

...or even (if it is safe to keep the references to x and y alive):

UGMISC_DECL_MEMBER_ACCESS(Access, foo); // Declares a foo accessor called Access.
auto caller = member_caller<Access>::fallback( get_default )(x, y);
auto val = caller(1, 2);

Member Function Documentation

fallback()

template<class Access>

template<class F>

constexpr default_function< F > ugmisc::member_caller< Access >::fallback ( F && f )

inlinestaticconstexpr

Parameters

f	A function or other callable which provides a default value if none of the objects can be called.

with()

template<class Access>

template<class... T>

constexpr wrapped_objects< void, T... > ugmisc::member_caller< Access >::with ( T &&... objs )

inlinestaticconstexpr

Parameters

objs	Objects to try calling.

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The documentation for this struct was generated from the following file:

• ugmisc/member.hpp