1<html> 2<head> 3<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"> 4<title>Store an Attribute Value into a Container after a Parser Produced a Value (Qi)</title> 5<link rel="stylesheet" href="../../../../../../../../doc/src/boostbook.css" type="text/css"> 6<meta name="generator" content="DocBook XSL Stylesheets V1.79.1"> 7<link rel="home" href="../../../../index.html" title="Spirit 2.5.8"> 8<link rel="up" href="../assign_to.html" title="Store a Parsed Attribute Value (Qi)"> 9<link rel="prev" href="assign_to_attribute_from_value.html" title="Store an Attribute Value after a Parser Produced a Value (Qi)"> 10<link rel="next" href="../store_value.html" title="Store Parsed Attribute Values into a Container (Qi)"> 11</head> 12<body bgcolor="white" text="black" link="#0000FF" vlink="#840084" alink="#0000FF"> 13<table cellpadding="2" width="100%"><tr> 14<td valign="top"><img alt="Boost C++ Libraries" width="277" height="86" src="../../../../../../../../boost.png"></td> 15<td align="center"><a href="../../../../../../../../index.html">Home</a></td> 16<td align="center"><a href="../../../../../../../../libs/libraries.htm">Libraries</a></td> 17<td align="center"><a href="http://www.boost.org/users/people.html">People</a></td> 18<td align="center"><a href="http://www.boost.org/users/faq.html">FAQ</a></td> 19<td align="center"><a href="../../../../../../../../more/index.htm">More</a></td> 20</tr></table> 21<hr> 22<div class="spirit-nav"> 23<a accesskey="p" href="assign_to_attribute_from_value.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../assign_to.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../store_value.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 24</div> 25<div class="section"> 26<div class="titlepage"><div><div><h5 class="title"> 27<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value"></a><a class="link" href="assign_to_container_from_value.html" title="Store an Attribute Value into a Container after a Parser Produced a Value (Qi)">Store 28 an Attribute Value into a Container after a Parser Produced a Value (Qi)</a> 29</h5></div></div></div> 30<h6> 31<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h0"></a> 32 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.assign_to_container_from_value"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.assign_to_container_from_value">assign_to_container_from_value</a> 33 </h6> 34<p> 35 The template <code class="computeroutput"><span class="identifier">assign_to_container_from_value</span></code> 36 is a type used as an attribute customization point. It is invoked by 37 all primitive <span class="emphasis"><em>Qi</em></span> parsers in order to store a parsed 38 attribute value into the attribute instance provided by the user, if 39 this attribute is a container type (<code class="computeroutput"><span class="identifier">is_container</span><span class="special"><</span><span class="identifier">T</span><span class="special">>::</span><span class="identifier">type</span></code> 40 evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>, where <code class="computeroutput"><span class="identifier">T</span></code> 41 is the attribute type). 42 </p> 43<h6> 44<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h1"></a> 45 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.module_headers"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.module_headers">Module 46 Headers</a> 47 </h6> 48<pre class="programlisting"><span class="preprocessor">#include</span> <span class="special"><</span><span class="identifier">boost</span><span class="special">/</span><span class="identifier">spirit</span><span class="special">/</span><span class="identifier">home</span><span class="special">/</span><span class="identifier">qi</span><span class="special">/</span><span class="identifier">detail</span><span class="special">/</span><span class="identifier">assign_to</span><span class="special">.</span><span class="identifier">hpp</span><span class="special">></span> 49</pre> 50<p> 51 Also, see <a class="link" href="../../../structure/include.html" title="Include">Include Structure</a>. 52 </p> 53<div class="note"><table border="0" summary="Note"> 54<tr> 55<td rowspan="2" align="center" valign="top" width="25"><img alt="[Note]" src="../../../../images/note.png"></td> 56<th align="left">Note</th> 57</tr> 58<tr><td align="left" valign="top"><p> 59 This header file does not need to be included directly by any user 60 program as it is normally included by other Spirit header files relying 61 on its content. 62 </p></td></tr> 63</table></div> 64<h6> 65<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h2"></a> 66 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.namespace"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.namespace">Namespace</a> 67 </h6> 68<div class="informaltable"><table class="table"> 69<colgroup><col></colgroup> 70<thead><tr><th> 71 <p> 72 Name 73 </p> 74 </th></tr></thead> 75<tbody><tr><td> 76 <p> 77 <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">spirit</span><span class="special">::</span><span class="identifier">traits</span></code> 78 </p> 79 </td></tr></tbody> 80</table></div> 81<h6> 82<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h3"></a> 83 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.synopsis"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.synopsis">Synopsis</a> 84 </h6> 85<pre class="programlisting"><span class="keyword">template</span> <span class="special"><</span><span class="keyword">typename</span> <span class="identifier">Attrib</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">T</span><span class="special">,</span> <span class="keyword">typename</span> <span class="identifier">Enable</span><span class="special">></span> 86<span class="keyword">struct</span> <span class="identifier">assign_to_container_from_value</span> 87<span class="special">{</span> 88 <span class="keyword">static</span> <span class="keyword">void</span> <span class="identifier">call</span><span class="special">(</span><span class="identifier">T</span> <span class="keyword">const</span><span class="special">&</span> <span class="identifier">val</span><span class="special">,</span> <span class="identifier">Attrib</span><span class="special">&</span> <span class="identifier">attr</span><span class="special">);</span> 89<span class="special">};</span> 90</pre> 91<h6> 92<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h4"></a> 93 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.template_parameters"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.template_parameters">Template 94 parameters</a> 95 </h6> 96<div class="informaltable"><table class="table"> 97<colgroup> 98<col> 99<col> 100<col> 101</colgroup> 102<thead><tr> 103<th> 104 <p> 105 Parameter 106 </p> 107 </th> 108<th> 109 <p> 110 Description 111 </p> 112 </th> 113<th> 114 <p> 115 Default 116 </p> 117 </th> 118</tr></thead> 119<tbody> 120<tr> 121<td> 122 <p> 123 <code class="computeroutput"><span class="identifier">Attrib</span></code> 124 </p> 125 </td> 126<td> 127 <p> 128 The type, <code class="computeroutput"><span class="identifier">Attrib</span></code> 129 is the type of the attribute as passed in by the user. This 130 type is a container type (<code class="computeroutput"><span class="identifier">is_container</span><span class="special"><</span><span class="identifier">Attrib</span><span class="special">>::</span><span class="identifier">type</span></code> 131 evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>). 132 </p> 133 </td> 134<td> 135 <p> 136 none 137 </p> 138 </td> 139</tr> 140<tr> 141<td> 142 <p> 143 <code class="computeroutput"><span class="identifier">T</span></code> 144 </p> 145 </td> 146<td> 147 <p> 148 The type, <code class="computeroutput"><span class="identifier">T</span></code> 149 is the type of the attribute instance as produced by the parser. 150 </p> 151 </td> 152<td> 153 <p> 154 none 155 </p> 156 </td> 157</tr> 158<tr> 159<td> 160 <p> 161 <code class="computeroutput"><span class="identifier">Enable</span></code> 162 </p> 163 </td> 164<td> 165 <p> 166 Helper template parameter usable to selectively enable or disable 167 certain specializations of <code class="computeroutput"><span class="identifier">assign_to_container_from_value</span></code> 168 utilizing SFINAE (i.e. <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">enable_if</span></code> 169 or <code class="computeroutput"><span class="identifier">boost</span><span class="special">::</span><span class="identifier">disable_if</span></code>). 170 </p> 171 </td> 172<td> 173 <p> 174 <code class="computeroutput"><span class="keyword">void</span></code> 175 </p> 176 </td> 177</tr> 178</tbody> 179</table></div> 180<div class="variablelist"> 181<p class="title"><b>Notation</b></p> 182<dl class="variablelist"> 183<dt><span class="term"><code class="computeroutput"><span class="identifier">Attrib</span></code></span></dt> 184<dd><p> 185 A type to be used as the target to store the attribute value in. 186 This type is guaranteed to be a container type (<code class="computeroutput"><span class="identifier">is_container</span><span class="special"><</span><span class="identifier">Attrib</span><span class="special">>::</span><span class="identifier">type</span></code> 187 evaluates to <code class="computeroutput"><span class="identifier">mpl</span><span class="special">::</span><span class="identifier">true_</span></code>). 188 </p></dd> 189<dt><span class="term"><code class="computeroutput"><span class="identifier">attr</span></code></span></dt> 190<dd><p> 191 An attribute instance of type <code class="computeroutput"><span class="identifier">Attrib</span></code>. 192 </p></dd> 193<dt><span class="term"><code class="computeroutput"><span class="identifier">T</span></code></span></dt> 194<dd><p> 195 A type as produced by the parser. The parser temporarily stores 196 its parsed values using this type. 197 </p></dd> 198<dt><span class="term"><code class="computeroutput"><span class="identifier">t</span></code></span></dt> 199<dd><p> 200 An attribute instance of type <code class="computeroutput"><span class="identifier">T</span></code>. 201 </p></dd> 202</dl> 203</div> 204<h6> 205<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h5"></a> 206 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.expression_semantics"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.expression_semantics">Expression 207 Semantics</a> 208 </h6> 209<div class="informaltable"><table class="table"> 210<colgroup> 211<col> 212<col> 213</colgroup> 214<thead><tr> 215<th> 216 <p> 217 Expression 218 </p> 219 </th> 220<th> 221 <p> 222 Semantics 223 </p> 224 </th> 225</tr></thead> 226<tbody><tr> 227<td> 228 <p> 229</p> 230<pre xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" class="table-programlisting"><span class="identifier">assign_to_container_from_value</span><span class="special"><</span><span class="identifier">Attrib</span><span class="special">,</span> <span class="identifier">T</span><span class="special">>::</span><span class="identifier">call</span><span class="special">(</span><span class="identifier">t</span><span class="special">,</span> <span class="identifier">attr</span><span class="special">)</span></pre> 231<p> 232 </p> 233 </td> 234<td> 235 <p> 236 Add the value <code class="computeroutput"><span class="identifier">t</span></code> 237 to the container attribute <code class="computeroutput"><span class="identifier">attr</span></code>. 238 </p> 239 </td> 240</tr></tbody> 241</table></div> 242<h6> 243<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h6"></a> 244 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.predefined_specializations"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.predefined_specializations">Predefined 245 Specializations</a> 246 </h6> 247<div class="informaltable"><table class="table"> 248<colgroup> 249<col> 250<col> 251</colgroup> 252<thead><tr> 253<th> 254 <p> 255 Template Parameters 256 </p> 257 </th> 258<th> 259 <p> 260 Semantics 261 </p> 262 </th> 263</tr></thead> 264<tbody> 265<tr> 266<td> 267 <p> 268 <code class="computeroutput"><span class="identifier">Attrib</span></code>, <code class="computeroutput"><span class="identifier">T</span></code> 269 </p> 270 </td> 271<td> 272 <p> 273 Add the argument <code class="computeroutput"><span class="identifier">t</span></code> 274 to <code class="computeroutput"><span class="identifier">attr</span></code>. 275 </p> 276 </td> 277</tr> 278<tr> 279<td> 280 <p> 281 <code class="computeroutput"><span class="identifier">unused_type</span></code>, 282 <code class="computeroutput"><span class="identifier">T</span></code> 283 </p> 284 </td> 285<td> 286 <p> 287 Do nothing. 288 </p> 289 </td> 290</tr> 291</tbody> 292</table></div> 293<h6> 294<a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.h7"></a> 295 <span class="phrase"><a name="spirit.advanced.customize.assign_to.assign_to_container_from_value.when_to_implement"></a></span><a class="link" href="assign_to_container_from_value.html#spirit.advanced.customize.assign_to.assign_to_container_from_value.when_to_implement">When 296 to implement</a> 297 </h6> 298<p> 299 The customization point <code class="computeroutput"><span class="identifier">assign_to_container_from_value</span></code> 300 needs to be implemented for a specific type whenever the default implementation 301 as shown above is not applicable. Examples for this could be that the 302 type <code class="computeroutput"><span class="identifier">Attrib</span></code> is not copy 303 constructible. 304 </p> 305</div> 306<table xmlns:rev="http://www.cs.rpi.edu/~gregod/boost/tools/doc/revision" width="100%"><tr> 307<td align="left"></td> 308<td align="right"><div class="copyright-footer">Copyright © 2001-2011 Joel de Guzman, Hartmut Kaiser<p> 309 Distributed under the Boost Software License, Version 1.0. (See accompanying 310 file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>) 311 </p> 312</div></td> 313</tr></table> 314<hr> 315<div class="spirit-nav"> 316<a accesskey="p" href="assign_to_attribute_from_value.html"><img src="../../../../../../../../doc/src/images/prev.png" alt="Prev"></a><a accesskey="u" href="../assign_to.html"><img src="../../../../../../../../doc/src/images/up.png" alt="Up"></a><a accesskey="h" href="../../../../index.html"><img src="../../../../../../../../doc/src/images/home.png" alt="Home"></a><a accesskey="n" href="../store_value.html"><img src="../../../../../../../../doc/src/images/next.png" alt="Next"></a> 317</div> 318</body> 319</html> 320
