op_arrow.md

operator->

• iterator[meta header]
• std[meta namespace]
• reverse_iterator[meta class]
• function[meta id-type]

pointer operator->() const;           // C++03
constexpr pointer operator->() const; // C++17
constexpr pointer operator->() const  // C++20
  requires (is_pointer_v<Iterator> ||
            requires (const Iterator i) { i.operator->(); });

• is_pointer_v[link /reference/type_traits/is_pointer.md]

概要

イテレータを通してオブジェクトにアクセスする

戻り値

• C++03 : &(operator*())

• C++14 : addressof(operator*())

• C++20 : 次のいずれか

  • Iteratorがポインタ型である場合

  return prev(current);

  • prev[link /reference/iterator/prev.md]
  • それ以外の場合

  return prev(current).operator->();

  • prev[link /reference/iterator/prev.md]

例

#include <iostream>
#include <vector>
#include <iterator>

class value {
  int x;

public:
  value(int x = 0) : x(x) {}
  int get() const { return x; }
};

int main()
{
  std::vector<value> v = {1, 2, 3};

  std::reverse_iterator<decltype(v)::iterator> it(v.end());

  int result = it->get();

  std::cout << result << std::endl;
}

• it->[color ff0000]

出力

3

参照

• LWG Issue 2188. Reverse iterator does not fully support targets that overload operator&
• P0031R0 A Proposal to Add Constexpr Modifiers to reverse_iterator, move_iterator, array and Range Access
• P0896R4 The One Ranges Proposal (was Merging the Ranges TS)