static_member_value< Access, T > Struct Template Reference

#include <ugmisc/member.hpp>

Public Types
using	safe_matched_type = ???
using	matched_type = ???

Static Public Member Functions
template<class F, class... A>
static constexpr decltype(auto)	get (F &&default_get, A &&...args)
static constexpr auto &	get ()

Static Public Attributes
static constexpr bool	has_member = ???

Detailed Description

template<class Access, class... T>
struct static_member_value< Access, T >

Finds a reference to a named static member value in the first type among T... which has a static value accessible by that name.

The Access is responsible for knowing the name to use, and is a type declared with the help of the UGMISC_DECL_MEMBER_ACCESS macro.

For example:

UGMISC_DECL_MEMBER_ACCESS(FooAccessor, foo); // Declares FooAccessor.
 
using Getter = static_member_value<FooAccessor, X, Y>;
 
auto& foo1 = Getter::get(); // Error if Getter::has_member is false.
decltype(auto) foo2 = Getter::get( defaultFoo, 1, 2 );

In the example above, the value of foo1 will be the first of the following which is valid:

1. A reference to X::foo.
2. A reference to Y::foo.

If neither of those is valid, the declaration is an error.

The value of foo2 will be the first valid value of the following:

1. The same as foo1
2. defaultFoo(1, 2)

Template Parameters

Access	A type declared using UGMISC_DECL_MEMBER_ACCESS. This is responsible for accessing the correctly named static member, according to the second argument passed to the macro.
T	The types in which to look for the named member.

Member Typedef Documentation

matched_type

template<class Access, class... T>

using static_member_value< Access, T >::matched_type = ???

The type whose named static member would be referenced by get(), if there is one. This member type is not declared if has_member is false.

safe_matched_type

template<class Access, class... T>

using static_member_value< Access, T >::safe_matched_type = ???

The type whose named static member would be referenced by get(), if there is one, or void if there is not.

See also

matched_type, has_member

Member Function Documentation

get() [1/2]

template<class Access, class... T>

constexpr auto & static_member_value< Access, T >::get ( )

inlinestaticconstexpr

Returns

A reference to the found static member.

See also

get(F&& default_get, A&&...args)

get() [2/2]

template<class Access, class... T>

template<class F, class... A>

constexpr decltype(auto) static_member_value< Access, T >::get ( F && default_get, A &&... args )

staticconstexpr

Like get() but with a default value. The value is provided by a callable parameter, which is passed the args.

This way side effects of getting the default value can be avoided if it is not needed.

Parameters

default_get	A function or callable object.
args	Optional arguments to pass to default_get.

Member Data Documentation

has_member

template<class Access, class... T>

bool static_member_value< Access, T >::has_member = ???

staticconstexpr

true if one of the types in T... has a member value accessed by Access.

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

• ugmisc/member.hpp