[#FOLLY_INVOKE_MEMBER]
= FOLLY_INVOKE_MEMBER
:mrdocs:

* FOLLY_INVOKE_MEMBER

== Synopsis

Declared in `<folly/functional/Invoke.h>`

[source,cpp,subs="verbatim,replacements,macros,-callouts"]
----
#define FOLLY_INVOKE_MEMBER(membername)

----

== Description

An invoker expression resulting in an invocable which, when invoked, invokes the member on the object with the given arguments.

Example:

FOLLY_INVOKE_MEMBER(find)(map, key)

Equivalent to:

map.find(key)

But also equivalent to:

std::invoke(FOLLY_INVOKE_MEMBER(find), map, key)

As an implementation detail, the resulting callable uses a lambda. This has two observable consequences. * Since C++17 only, lambda invocations may be marked constexpr. * Since C++20 only, lambda definitions may appear in an unevaluated context, namely, in an operand to decltype, noexcept, sizeof, or typeid.

== Parameters

[cols="1,4"]
|===
| Name| Description
| *membername*
| the member name to invoke on the object
|===


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