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最終更新日時(UTC):
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<div class="identifier-type">function</div><div class="header"><sstream></div><h1 itemprop="name"><span class="namespace" title="namespace std">std::</span><span class="class" title="class basic_stringstream">basic_stringstream::</span><span class="token">str</span></h1>
<div itemprop="articleBody"><p><div class="codehilite"><pre><span></span><code><span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">Allocator</span><span class="o">></span><span class="w"> </span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="p">;</span><span class="w"> </span><span class="c1">// (1) C++03</span>
<span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">Allocator</span><span class="o">></span><span class="w"> </span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="o">&</span><span class="p">;</span><span class="w"> </span><span class="c1">// (1) C++20</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">SAlloc</span><span class="o">></span>
<span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">SAlloc</span><span class="o">></span><span class="w"> </span><span class="n">str</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n">SAlloc</span><span class="o">&</span><span class="w"> </span><span class="n">sa</span><span class="p">)</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="o">&</span><span class="p">;</span><span class="w"> </span><span class="c1">// (2) C++20</span>
<span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">Allocator</span><span class="o">></span><span class="w"> </span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="k">const</span><span class="w"> </span><span class="o">&&</span><span class="p">;</span><span class="w"> </span><span class="c1">// (3) C++20</span>
<span class="kt">void</span><span class="w"> </span><span class="nf">str</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">Allocator</span><span class="o">>&</span><span class="w"> </span><span class="n">s</span><span class="p">);</span><span class="w"> </span><span class="c1">// (4) C++03</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">SAlloc</span><span class="o">></span>
<span class="kt">void</span><span class="w"> </span><span class="n">str</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">SAlloc</span><span class="o">>&</span><span class="w"> </span><span class="n">s</span><span class="p">);</span><span class="w"> </span><span class="c1">// (5) C++20</span>
<span class="kt">void</span><span class="w"> </span><span class="nf">str</span><span class="p">(</span><span class="k">const</span><span class="w"> </span><span class="n"><a href="../../string/basic_string.html">basic_string</a></span><span class="o"><</span><span class="n">CharT</span><span class="p">,</span><span class="w"> </span><span class="n">Traits</span><span class="p">,</span><span class="w"> </span><span class="n">Allocator</span><span class="o">>&&</span><span class="w"> </span><span class="n">s</span><span class="p">);</span><span class="w"> </span><span class="c1">// (6) C++20</span>
<span class="k">template</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="kt">void</span><span class="w"> </span><span class="n">str</span><span class="p">(</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">t</span><span class="p">);</span><span class="w"> </span><span class="c1">// (7) C++26</span>
</code></pre></div>
</p>
<h2>概要</h2>
<p>文字列オブジェクトを取得または設定する。</p>
<p>書き込み位置としては先頭にリセットされるため注意すること。</p>
<ul>
<li>(1) : 文字列オブジェクトを取得する</li>
<li>(2) : 文字列オブジェクトを取得して、<code>SAlloc</code>型のアロケータ<code>sa</code>によって確保する</li>
<li>(3) : 保持する文字列オブジェクトをムーブして取得する</li>
<li>(4) : 文字列オブジェクト<code>s</code>を設定する</li>
<li>(5) : <code>Allocator</code>に変換可能な<code>SAlloc</code>型のアロケータによって確保されているデータをコピーして、文字列オブジェクト<code>s</code>を設定する</li>
<li>(6) : 与えられた文字列オブジェクト<code>s</code>をムーブして設定する</li>
<li>(7) : <code><a href="../../string_view/basic_string_view.html">std::basic_string_view</a></code>に変換可能な文字列を設定する</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。Constraints。関数であればオーバーロード解決に参加するための条件、それ以外であれば受け付ける型の条件">テンプレートパラメータ制約</a></h2>
<ul>
<li>(7) : <code>is_convertible_v<const T&, basic_string_view<CharT, Traits>></code>が<code>true</code>であること</li>
</ul>
<h2>効果</h2>
<ul>
<li>(1) : <code>return rdbuf()->str()</code> と等価</li>
<li>(2) : <code>return rdbuf()->str(sa)</code> と等価</li>
<li>(3) : <code>return std::move(*rdbuf()).str()</code> と等価</li>
<li>(4) : <code>rdbuf()->str(s)</code> と等価</li>
<li>(5) : <code>rdbuf()->str(s)</code> と等価</li>
<li>(6) : <code>rdbuf()->str(std::move(s))</code> と等価</li>
<li>(7) : <code>rdbuf()->str(t)</code> と等価</li>
</ul>
<h2>例</h2>
<h3>基本的な使い方</h3>
<p><div class="yata" id="f878ec91e348a6b57d9e78dc958fe7a9a63169e7"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../../sstream.html"><sstream></a></span>
<span class="cp">#include <a href="../../string.html"><string></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="n">std</span><span class="o">::</span><span class="n">stringstream</span><span class="w"> </span><span class="n">ss</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 文字列を設定</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">(</span><span class="s">"initial content"</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"1: "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// ストリームに追記</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n"><a href="../../ostream/basic_ostream/seekp.html">seekp</a></span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n"><a href="../../ios/ios_base.html">std::ios_base</a></span><span class="o">::</span><span class="n"><a href="../../ios/ios_base/type-seekdir.html">end</a></span><span class="p">);</span>
<span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" + added"</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"2: "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 新しい文字列で置き換え</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">(</span><span class="s">"new content"</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"3: "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 読み取り位置に注意</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">word</span><span class="p">;</span>
<span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o">>></span><span class="w"> </span><span class="n">word</span><span class="p">;</span><span class="w"> </span><span class="c1">// "new"を読む</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"Read: "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">word</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"4: "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span><span class="w"> </span><span class="c1">// 全体は変わらない</span>
<span class="w"> </span><span class="c1">// 空文字列でクリア</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">(</span><span class="s">""</span><span class="p">);</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">"5: Empty? "</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="p">(</span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">().</span><span class="n">empty</span><span class="p">()</span><span class="w"> </span><span class="o">?</span><span class="w"> </span><span class="s">"yes"</span><span class="w"> </span><span class="o">:</span><span class="w"> </span><span class="s">"no"</span><span class="p">)</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code>1: initial content
2: initial content + added
3: new content
Read: new
4: new content
5: Empty? yes
</code></pre></p>
<h4>ムーブを使用する例 (C++20)</h4>
<p><div class="yata" id="a853b83aaa9c57896e46fda97494f4316353ca6a"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../../sstream.html"><sstream></a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">stringstream</span><span class="w"> </span><span class="n">ss</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// ムーブして文字列を設定</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">s</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"Move string"</span><span class="p">;</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">(</span><span class="n">std</span><span class="o">::</span><span class="n">move</span><span class="p">(</span><span class="n">s</span><span class="p">));</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">seekp</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ios_base</span><span class="o">::</span><span class="n">end</span><span class="p">);</span><span class="w"> </span><span class="c1">// 書き込み位置を末尾に移動</span>
<span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" more"</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// ムーブで文字列を取得</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">std</span><span class="o">::</span><span class="n">move</span><span class="p">(</span><span class="n">ss</span><span class="p">).</span><span class="n">str</span><span class="p">();</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</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"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code>Move string more
Move string more
</code></pre></p>
<h3>string_viewからの設定 (C++26)</h3>
<p><div class="yata" id="c4bf4ede3a14862bd6dc3bef0b45604c6e509a26"><div class="codehilite"><pre><span></span><code><span class="cp">#include <a href="../../iostream.html"><iostream></a></span>
<span class="cp">#include <a href="../../sstream.html"><sstream></a></span>
<span class="cp">#include <a href="../../string_view.html"><string_view></a></span>
<span class="kt">int</span><span class="w"> </span><span class="nf">main</span><span class="p">()</span><span class="w"> </span><span class="p">{</span>
<span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">stringstream</span><span class="w"> </span><span class="n">ss</span><span class="p">;</span>
<span class="w"> </span><span class="c1">// 文字列リテラルを設定</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">(</span><span class="s">"set from string literal"</span><span class="p">);</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">seekp</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ios_base</span><span class="o">::</span><span class="n">end</span><span class="p">);</span><span class="w"> </span><span class="c1">// 書き込み位置を末尾に移動</span>
<span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" test"</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="w"> </span><span class="c1">// <a href="../../string_view/basic_string_view.html">string_view</a>を設定</span>
<span class="w"> </span><span class="n"><a href="../../string_view/basic_string_view.html">std::string_view</a></span><span class="w"> </span><span class="n">sv</span><span class="w"> </span><span class="o">=</span><span class="w"> </span><span class="s">"set from <a href="../../string_view/basic_string_view.html">string_view</a>"</span><span class="p">;</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">(</span><span class="n">sv</span><span class="p">);</span>
<span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">seekp</span><span class="p">(</span><span class="mi">0</span><span class="p">,</span><span class="w"> </span><span class="n">std</span><span class="o">::</span><span class="n">ios_base</span><span class="o">::</span><span class="n">end</span><span class="p">);</span><span class="w"> </span><span class="c1">// 書き込み位置を末尾に移動</span>
<span class="w"> </span><span class="n">ss</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="s">" test"</span><span class="p">;</span>
<span class="w"> </span><span class="n"><a href="../../iostream/cout.html">std::cout</a></span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n">ss</span><span class="p">.</span><span class="n">str</span><span class="p">()</span><span class="w"> </span><span class="o"><<</span><span class="w"> </span><span class="n"><a href="../../ostream/endl.html">std::endl</a></span><span class="p">;</span>
<span class="p">}</span>
</code></pre></div>
</div></p>
<h4>出力</h4>
<p><pre><code>set from string literal test
set from <a href="../../string_view/basic_string_view.html">string_view</a> test
</code></pre></p>
<h2>関連項目</h2>
<ul>
<li><code><a href="../basic_stringbuf/str.html">basic_stringbuf::str</a></code></li>
</ul>
<h2>参照</h2>
<ul>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2019/p0408r7.pdf" target="_blank">P0408R7 Efficient Access to <code>basic_stringbuf</code>'s Buffer</a></li>
<li><a href="https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2023/p2495r3.pdf" target="_blank">P2495R3 Interfacing stringstreams with <code>string_view</code></a><ul>
<li>C++26で<code><a href="../../string_view/basic_string_view.html">std::string_view</a></code>に対応した</li>
</ul>
</li>
</ul></div>
</div>
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