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<html><!-- #BeginTemplate "/Templates/tmpl.dwt" --><!-- DW6 --><head><!-- #BeginEditable "doctitle" --> <title>PTypes: string: constructors/destructors</title><!-- #EndEditable --> <meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1"><link rel="stylesheet" href="styles.css"></head><body bgcolor="#FFFFFF" leftmargin="40" marginwidth="40"><p><a href="../index.html"><img src="title-20.png" width="253" height="39" alt="C++ Portable Types Library (PTypes) Version 2.0" border="0"></a> <hr size="1" noshade><!-- #BeginEditable "body" --> <p class="hpath"><a href="index.html">Top</a>: <a href="basic.html">Basic types</a>: <a href="string.html">string</a>: Constructors/destructors</p><blockquote> <pre class="lang">#include <ptypes.h>class string { string(); string(const string&); string(char); string(const char*); string(const char*, int); ~string();}</pre></blockquote><p>A string object can be constructed in 5 different ways:</p><ul><li> <p> default constructor <span class="lang">string()</span> creates an empty string.</p></li><li> <p>copy constructor <span class="lang">string(const string& s)</span> creates a copy of the given string <span class="lang">s</span>. Actually this constructor only increments the reference count by 1 and no memory allocation takes place.</p></li><li> <p><span class="def">string(char c)</span> constructs a new string consisting of one character <span class="lang">c</span>.</p></li><li> <p><span class="def">string(const char* s)</span> constructs a new string object from a null-terminated string. If <span class="lang">s</span> is either <span class="lang">NULL</span> or is a pointer to a null character, an empty string object is created. This constructor can be used to assign a string literal to a string object (see examples below).</p></li><li> <p><span class="def">string(const char* s, int len)</span> copies <span class="lang">len</span> bytes of data from buffer <span class="lang">s</span> to the newly allocated string buffer.</p></li></ul><p>Destructor <span class="lang">~string()</span> decrements the reference count for the given string buffer and removes it from the dynamic memory if necessary.</p><p><b>Examples:</b></p><blockquote> <pre>string s1; <span class="comment">// empty string</span>string s2 = s1; <span class="comment">// copy</span>string s3 = 'A'; <span class="comment">// single character</span>string s4 = "ABCabc"; <span class="comment">// string literal</span>char* p = "ABCabc";string s5 = p; <span class="comment">// null-terminated string</span>string s6(p, 3); <span class="comment">// buffer/length</span></pre></blockquote><p class="seealso">See also: <a href="string.operators.html">Operators</a>, <a href="string.typecasts.html">Typecasts</a>, <a href="string.manipulation.html">Manipulation</a>, <a href="string.conversion.html">Conversion</a></p><!-- #EndEditable --><hr size="1"><a href="../index.html" class="ns">PTypes home</a></body><!-- #EndTemplate --></html>⌨️ 快捷键说明
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