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<header data-kunai-mdinfo="{"meta": {"header": ["any"], "namespace": ["std"], "id-type": ["function template"], "cpp": ["cpp17"]}, "sources": [{"id": "ed8591e974049297796278d25d2e62bc6960bc0d", "source": "#include <cassert>\n#include <any>\n#include <string>\n#include <utility>\n\nint main()\n{\n // (1)\n {\n const std::any x = 3;\n\n // \u30b3\u30d4\u30fc\u3092\u53d6\u308a\u51fa\u3059\n int r1 = std::any_cast<int>(x);\n assert(r1 == 3);\n\n // \u53c2\u7167\u3092\u53d6\u308a\u51fa\u3059\n const int& r2 = std::any_cast<const int&>(x);\n assert(r2 == 3);\n\n // x\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304c\u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u306fint\u578b\u3067\u3001long long\u578b\u306b\u5909\u63db\u53ef\u80fd\u3060\u304c\u3001\n // any_cast\u95a2\u6570\u306b\u306f\u76f4\u63a5\u306e\u578bint\u3092\u6307\u5b9a\u3057\u306a\u3051\u308c\u3070\u306a\u3089\u306a\u3044\n try {\n std::any_cast<long long>(x);\n assert(false);\n }\n catch (std::bad_any_cast& e) {\n // \u578b\u306e\u6307\u5b9a\u3092\u9593\u9055\u3046\u3068\u3001bad_any_cast\u4f8b\u5916\u304c\u9001\u51fa\u3055\u308c\u308b\n assert(true);\n }\n }\n\n // (2)\n {\n std::any x = std::string{\"Hello\"};\n\n // \u30b3\u30d4\u30fc\u3092\u53d6\u308a\u51fa\u3059\n std::string r1 = std::any_cast<std::string>(x);\n assert(r1 == \"Hello\");\n\n // \u53c2\u7167\u3092\u53d6\u308a\u51fa\u3059\n std::string& r2 = std::any_cast<std::string&>(x);\n assert(r2 == \"Hello\");\n }\n\n // (3)\n {\n std::any x = std::string{\"Hello\"};\n\n // any\u30af\u30e9\u30b9\u306e\u4e00\u6642\u30aa\u30d6\u30b8\u30a7\u30af\u30c8\u304b\u3089\u5024\u3092\u30e0\u30fc\u30d6\u3057\u3066\u53d6\u308a\u51fa\u3059\n std::string r = std::any_cast<std::string>(std::move(x));\n assert(r == \"Hello\");\n }\n\n // (4)\n {\n const std::any x = 3;\n\n // \u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u3078\u306e\u30dd\u30a4\u30f3\u30bf\u3092\u53d6\u308a\u51fa\u3059\n const int* p1 = std::any_cast<int>(&x);\n assert(*p1 == 3);\n\n // \u578b\u306e\u6307\u5b9a\u3092\u9593\u9055\u3046\u3068\u30cc\u30eb\u30dd\u30a4\u30f3\u30bf\u304c\u8fd4\u308b\n const long long* p2 = std::any_cast<long long>(&x);\n assert(p2 == nullptr);\n }\n\n // (5)\n {\n std::any x = 3;\n\n // \u4fdd\u6301\u3057\u3066\u3044\u308b\u5024\u3078\u306e\u30dd\u30a4\u30f3\u30bf\u3092\u53d6\u308a\u51fa\u3059\n int* p1 = std::any_cast<int>(&x);\n assert(*p1 == 3);\n\n // \u578b\u306e\u6307\u5b9a\u3092\u9593\u9055\u3046\u3068\u30cc\u30eb\u30dd\u30a4\u30f3\u30bf\u304c\u8fd4\u308b\n long long* p2 = std::any_cast<long long>(&x);\n assert(p2 == nullptr);\n }\n}\n"}], "page_id": ["reference", "any", "any_cast"]}">
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<div class="identifier-type">function template</div><div class="header"><any></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="token">any_cast</span><span class="cpp cpp17" title="C++17で追加">(C++17)</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="k">namespace</span><span class="w"> </span><span class="nn">std</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">any_cast</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="any.html">any</a></span><span class="o">&</span><span class="w"> </span><span class="n">operand</span><span class="p">);</span><span class="w"> </span><span class="c1">// (1)</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">any_cast</span><span class="p">(</span><span class="n"><a href="any.html">any</a></span><span class="o">&</span><span class="w"> </span><span class="n">operand</span><span class="p">);</span><span class="w"> </span><span class="c1">// (2)</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="w"> </span><span class="n">any_cast</span><span class="p">(</span><span class="n"><a href="any.html">any</a></span><span class="o">&&</span><span class="w"> </span><span class="n">operand</span><span class="p">);</span><span class="w"> </span><span class="c1">// (3)</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n">T</span><span class="o">*</span><span class="w"> </span><span class="n">any_cast</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="any.html">any</a></span><span class="o">*</span><span class="w"> </span><span class="n">operand</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (4)</span>
<span class="w"> </span><span class="k">template</span><span class="w"> </span><span class="o"><</span><span class="k">class</span><span class="w"> </span><span class="nc">T</span><span class="o">></span>
<span class="w"> </span><span class="n">T</span><span class="o">*</span><span class="w"> </span><span class="n">any_cast</span><span class="p">(</span><span class="n"><a href="any.html">any</a></span><span class="o">*</span><span class="w"> </span><span class="n">operand</span><span class="p">)</span><span class="w"> </span><span class="k">noexcept</span><span class="p">;</span><span class="w"> </span><span class="c1">// (5)</span>
<span class="p">}</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p><code><a href="any.html">std::any</a></code>オブジェクトが保持している値を取り出す。この関数に指定する型は、<code>any</code>オブジェクトが保持している値が変換可能な型ではなく、保持している値の型と (<code>const</code>/参照の修飾を除いて) 同じでなければならない。</p>
<ul>
<li>(1), (2), (3) : <code>std::any</code>オブジェクトが保持している型を指定して、その値のコピーまたは参照を取得する。コピーで取り出す場合は<code>any_cast<int>(x)</code>、参照で取り出す場合は<code>any_cast<int&>(x)</code>のように指定する。型の指定を間違った場合は<a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>が送出される</li>
<li>(4), (5) : <code>std::any</code>オブジェクトが保持している型を指定して、その値を指すポインタを取得する。型の指定を間違った場合はヌルポインタが返る</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="関数等の意味論を構成する要素の1つ。Mandates。満たさなければプログラムが不適格となる要件。この要件は、オーバーロード解決によって選択された関数内での`static_assert`の定数条件式や、関数に対するdelete宣言などで表現できる">適格要件</a></h2>
<p><code>using U = <a href="../type_traits/remove_cv.html">remove_cv_t</a><<a href="../type_traits/remove_reference.html">remove_reference_t</a><T>>;</code>であるとして、</p>
<ul>
<li>(1) : <code><a href="../type_traits/is_constructible.html">is_constructible_v</a><T, const U&> == true</code>であること。そうでない場合、プログラムは<a class="cpprefjp-defined-word" data-desc="プログラムが適格でないこと。コンパイルエラーなどになる" href="../../implementation-compliance.html#dfn-ill-formed">不適格</a>となる</li>
<li>(2) : <code><a href="../type_traits/is_constructible.html">is_constructible_v</a><T, U&> == true</code>であること。そうでない場合、プログラムは<a class="cpprefjp-defined-word" data-desc="プログラムが適格でないこと。コンパイルエラーなどになる" href="../../implementation-compliance.html#dfn-ill-formed">不適格</a>となる</li>
<li>(3) : <code><a href="../type_traits/is_constructible.html">is_constructible_v</a><T, U> == true</code>であること。そうでない場合、プログラムは<a class="cpprefjp-defined-word" data-desc="プログラムが適格でないこと。コンパイルエラーなどになる" href="../../implementation-compliance.html#dfn-ill-formed">不適格</a>となる</li>
<li>(4), (5) : <code><a href="../type_traits/is_void.html">is_void_v</a><T> == false</code>であること<ul>
<li>C++26から</li>
</ul>
</li>
</ul>
<h2>効果</h2>
<p><code>using U = <a href="../type_traits/remove_cv.html">remove_cv_t</a><<a href="../type_traits/remove_reference.html">remove_reference_t</a><T>>;</code>であるとして、</p>
<ul>
<li>(1), (2) : <code>operand</code>オブジェクトが保持している<code>U</code>型オブジェクトを返す</li>
<li>(3) : <code>operand</code>オブジェクトが保持している<code>U</code>型オブジェクトをムーブして返す</li>
<li>(4), (5) : <code>operand != nullptr</code>かつ<code><a href="any/type.html">operand->type()</a> == typeid(T)</code>である場合、<code>operand</code>が保持している<code>T</code>型オブジェクトへのポインタを返す</li>
</ul>
<h2><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a></h2>
<ul>
<li>(1), (2), (3) : <code><a href="any/type.html">operand.type()</a> != typeid(U)</code>である場合、<code><a href="bad_any_cast.html">bad_any_cast</a></code><a class="cpprefjp-defined-word" data-desc="問題が発生したときに、現在実行位置を過去に通過・記録した位置に戻し、文脈情報を添えて紐づけられた処理(例外ハンドラー)を呼び出す仕組み。またはその事態">例外</a>を送出する</li>
</ul>
<h2>例</h2>
<p><div class="yata" id="ed8591e974049297796278d25d2e62bc6960bc0d"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../cassert.html"><cassert></a></span>
<span class="cp">#include <a href="../any.html"><any></a></span>
<span class="cp">#include <a href="../string.html"><string></a></span>
<span class="cp">#include <a href="../utility.html"><utility></a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span>
<span class="p">{</span>
<span class="w"> </span><span class="c1">// (1)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="any.html">std::any</a></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// コピーを取り出す</span>
<span class="w"> </span><span class="kt">int</span><span class="w"> </span><span class="n">r1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">(</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">r1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 参照を取り出す</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="o">&</span><span class="w"> </span><span class="n">r2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="o">&></span><span class="p">(</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">r2</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// xオブジェクトが保持している値はint型で、long long型に変換可能だが、</span>
<span class="w"> </span><span class="c1">// any_cast関数には直接の型intを指定しなければならない</span>
<span class="w"> </span><span class="k">try</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="kt">long</span><span class="w"> </span><span class="kt">long</span><span class="o">></span><span class="p">(</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="nb">false</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="k">catch</span><span class="w"> </span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">bad_any_cast</span><span class="o">&</span><span class="w"> </span><span class="n">e</span><span class="p">)</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="c1">// 型の指定を間違うと、bad_any_cast例外が送出される</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="nb">true</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// (2)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="any.html">std::any</a></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="p">{</span><span class="s">"Hello"</span><span class="p">};</span>
<span class="w"> </span><span class="c1">// コピーを取り出す</span>
<span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">r1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">></span><span class="p">(</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">r1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">"Hello"</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 参照を取り出す</span>
<span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">&</span><span class="w"> </span><span class="n">r2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">&></span><span class="p">(</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">r2</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">"Hello"</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// (3)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="any.html">std::any</a></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="p">{</span><span class="s">"Hello"</span><span class="p">};</span>
<span class="w"> </span><span class="c1">// anyクラスの一時オブジェクトから値をムーブして取り出す</span>
<span class="w"> </span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="w"> </span><span class="n">r</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="n"><a href="../string/basic_string.html">std::string</a></span><span class="o">></span><span class="p">(</span><span class="n"><a href="../utility/move.html">std::move</a></span><span class="p">(</span><span class="n">x</span><span class="p">));</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">r</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="s">"Hello"</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// (4)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="n"><a href="any.html">std::any</a></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 保持している値へのポインタを取り出す</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">(</span><span class="o">&</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 型の指定を間違うとヌルポインタが返る</span>
<span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="kt">long</span><span class="o">*</span><span class="w"> </span><span class="n">p2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="kt">long</span><span class="w"> </span><span class="kt">long</span><span class="o">></span><span class="p">(</span><span class="o">&</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p2</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="w"> </span><span class="c1">// (5)</span>
<span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n"><a href="any.html">std::any</a></span><span class="w"> </span><span class="n">x</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="mi">3</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 保持している値へのポインタを取り出す</span>
<span class="w"> </span><span class="kt">int</span><span class="o">*</span><span class="w"> </span><span class="n">p1</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="kt">int</span><span class="o">></span><span class="p">(</span><span class="o">&</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="o">*</span><span class="n">p1</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="mi">3</span><span class="p">);</span>
<span class="w"> </span><span class="c1">// 型の指定を間違うとヌルポインタが返る</span>
<span class="w"> </span><span class="kt">long</span><span class="w"> </span><span class="kt">long</span><span class="o">*</span><span class="w"> </span><span class="n">p2</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="n"><span style="color:#ff0000">std::any_cast</span></span><span class="o"><</span><span class="kt">long</span><span class="w"> </span><span class="kt">long</span><span class="o">></span><span class="p">(</span><span class="o">&</span><span class="n">x</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../cassert/assert.html">assert</a></span><span class="p">(</span><span class="n">p2</span><span class="w"> </span><span class="o">==</span><span class="w"> </span><span class="nb">nullptr</span><span class="p">);</span>
<span class="w"> </span><span class="p">}</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h3>出力</h3>
<p><pre><code></code></pre></p>
<h2>バージョン</h2>
<h3>言語</h3>
<ul>
<li>C++17</li>
</ul>
<h3>処理系</h3>
<ul>
<li><a href="../../implementation.html#clang">Clang</a>: 4.0.1 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#gcc">GCC</a>: 7.3 <span aria-label="検証済" role="img" title="検証済">✅</span></li>
<li><a href="../../implementation.html#visual_cpp">Visual C++</a>: ??</li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://cplusplus.github.io/LWG/issue3305" target="_blank">LWG Issue 3305. <code>any_cast<void></code></a></li>
</ul></div>
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