content/glyph/book/extending/params_attrs.html
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 |
<!DOCTYPE html>
<html lang="en">
<head>
<title>Glyph - Parameters and Attributes</title>
<meta charset="utf-8" />
<meta name="author" content="Fabio Cevasco" />
<meta name="copyright" content="Fabio Cevasco" />
<meta name="robots" content="all, follow" />
<meta name="Revisit-After" content="2 Days" />
<meta name="language" content="en" />
<meta name="target_country" content="en-us" />
<meta name="country" content="United States" />
<meta name="description" content="H3RALD - Fabio Cevasco's Web Site" />
<meta name="keywords" content="h3rald, fabio cevasco, glyph" />
<link rel="shortcut icon" href="/favicon.png" type="image/png" />
<meta content="44.388041;9.073248" name="ICBM" />
<link rel="stylesheet" type="text/css" href="/styles/html5reset.css" />
<link rel="stylesheet" type="text/css" href="/styles/style.css" />
<!--[if lte IE 8]>
<script src="/js/html5.js" type="text/javascript"></script>
<![endif]-->
</head>
<body>
<!--[if lte IE 6]>
<div id="ie-warning">
This site is not compatible with Internet Explorer 6 or lower. You should consider using a more modern browser for a better – and <em>safer</em> – web experience. [<a href="http://browsehappy.com/browsers/">Read More »</a>]
</div>
<![endif]-->
<section id="container">
<header class="page">
<nav class="home-link">
<a href="/">
<img src="/images/h3rald_small.png" alt="H3RALD" class="default"/>
<![if !IE]>
<img src="/images/h3rald_hover_small.png" alt="H3RALD" class="hover"/>
<![endif]>
</a>
</nav>
<nav class="section">
/<a href="/projects/" rel="archives">PROJECTS</a>
</nav>
</header>
<article class="page">
<header>
<hgroup>
<h1>Parameters and Attributes</h1>
</hgroup>
</header>
<section id="body-text" class="hyphenate">
<nav><a href="/glyph/book/extending/macro_def.html">Defining Custom Macros ←</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/extending/bookmarks_headers.html">→ Bookmarks and Headers</a></nav>
<p>Perhaps the most common things to do in a macro definition is accessing parameters and attributes. When doing so, it is important to consider whether we want to retrieve the <em>raw value</em> of and attribute or parameter or its <em>expanded value</em>. The difference between the two will become clearer in the following sections and also in the <a href="/glyph/book/extending/interpreting.html#interpreting">Interpreting Glyph Code</a> section.</p>
<section class="section">
<header><h1 id="expanded_values">Accessing Expanded Values</h1></header>
<p>Normally, you just want to get the value of an attribute or parameter and use it in the macro. This means, in other words, its <em>expanded</em> value, i.e. the value resulting from the expansion of the macros (if any) within the attribute or parameter.</p>
<p>To access expanded values, use the following methods:</p>
<ul>
<li><code>parameter</code> (or <code>param</code>): Returns the expanded value of the parameter specified by number. Other parameters are not expanded.</li>
<li><code>value</code>: Returns the expanded value of the first parameter (i.e. like <code>parameter(0)</code>).</li>
<li><code>attribute</code> (or <code>attr</code>): Returns the expanded value of the attribute specified by name. Other attributes are not expanded.</li>
<li><code>parameters</code> (or <code>params</code>): Returns an array of expanded parameters.</li>
<li><code>attributes</code> (or <code>attrs</code>): Returns a hash of expanded attributes.</li>
</ul>
</section>
<section class="section">
<header><h1 id="h_77">Accessing Raw Values</h1></header>
<p>While accessing expanded values is simple and immediate, in some cases it may not produce the desired results. Consider the following macro definition:</p>
<div class="CodeRay">
<div class="code"><pre><span class="no"> 1</span> macro <span class="sy">:nest_section</span> <span class="r">do</span>
<span class="no"> 2</span> interpret <span class="s"><span class="dl">%{</span><span class="k">section[
<span class="no"> 3</span> @title[A]
<span class="no"> 4</span> section[
<span class="no"> 5</span> @title[B]
<span class="no"> 6</span> </span><span class="il"><span class="idl">#{</span>value<span class="idl">}</span></span><span class="k">
<span class="no"> 7</span> ]
<span class="no"> 8</span> ]</span><span class="dl">}</span></span>
<span class="no"> 9</span> <span class="r">end</span></pre></div>
</div>
<p>And suppose to use it as follows:</p>
<div class="CodeRay">
<div class="code"><pre><span class="no">1</span> nest_section[
<span class="no">2</span> section[
<span class="no">3</span> <span class="iv">@title</span>[<span class="co">Inner</span> <span class="co">Section</span>]
<span class="no">4</span> ...
<span class="no">5</span> ]
<span class="no">6</span> ]</pre></div>
</div>
<p>It produces the following HTML code:</p>
<div class="CodeRay">
<div class="code"><pre><span class="no"> 1</span> <span class="ta"><div</span> <span class="an">class</span>=<span class="s"><span class="dl">"</span><span class="k">section</span><span class="dl">"</span></span><span class="ta">></span>
<span class="no"> 2</span> <span class="ta"><h2</span> <span class="an">id</span>=<span class="s"><span class="dl">"</span><span class="k">h_2</span><span class="dl">"</span></span><span class="ta">></span>A<span class="ta"></h2></span>
<span class="no"> 3</span> <span class="ta"><div</span> <span class="an">class</span>=<span class="s"><span class="dl">"</span><span class="k">section</span><span class="dl">"</span></span><span class="ta">></span>
<span class="no"> 4</span> <span class="ta"><h3</span> <span class="an">id</span>=<span class="s"><span class="dl">"</span><span class="k">h_3</span><span class="dl">"</span></span><span class="ta">></span>B<span class="ta"></h3></span>
<span class="no"> 5</span> <span class="ta"><div</span> <span class="an">class</span>=<span class="s"><span class="dl">"</span><span class="k">section</span><span class="dl">"</span></span><span class="ta">></span>
<span class="no"> 6</span> <span class="ta"><h2</span> <span class="an">id</span>=<span class="s"><span class="dl">"</span><span class="k">h_1</span><span class="dl">"</span></span><span class="ta">></span>Inner Section<span class="ta"></h2></span>
<span class="no"> 7</span> ...
<span class="no"> 8</span> <span class="ta"></div></span>
<span class="no"> 9</span> <span class="ta"></div></span>
<span class="no"><strong>10</strong></span> <span class="ta"></div></span></pre></div>
</div>
<p>Everything is fine <em>except</em> for the header level: the heading "Inner Section" is of level 2, but it should be level 4!</p>
<p>This happens because the inner section is evaluated <em>before</em> the <code>nest_section</code> macro: after all, we ask for it ourselves when we call the <code>value</code> method inside the macro definition. When the value is expanded, there are no outer sections <em>yet</em>.</p>
<p>To avoid this unwanted behavior, we can use the <code>raw_value</code> method instead, that returns the first parameter converted back to a Glyph code string.</p>
<aside class="tip">
<span class="note-title">Tip</span>To be on the safe side, always use <code>raw_*</code> methods when interpreting.
</aside>
<p>To access raw values, use the following methods:</p>
<ul>
<li><code>raw_parameter</code> (or <code>raw_param</code>): Returns the raw parameter value of the parameter specified by number.</li>
<li><code>raw_value</code>: Returns the first raw parameter value (i.e. like <code>raw_parameter(0)</code>).</li>
<li><code>raw_attribute</code> (or <code>raw_attr</code>): Returns the attribute value of the attribute specified by name.</li>
</ul>
</section>
<nav><a href="/glyph/book/extending/macro_def.html">Defining Custom Macros ←</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/extending/bookmarks_headers.html">→ Bookmarks and Headers</a></nav>
</section>
</article>
<footer>
<section class="ads">
<script type="text/javascript"><!--
google_ad_client = "pub-2871497824158668";
/* 728x90, created 9/10/10 */
google_ad_slot = "3963343166";
google_ad_width = 728;
google_ad_height = 90;
//-->
</script>
<script type="text/javascript" src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
</script>
</section>
<section>
<nav>
<a href="/about/">ABOUT</a>|<a href="/contact/">CONTACT</a>
</nav>
<p>H3RALD Web Site v8.1 — © 2010 — <em>Fabio Cevasco</em></p>
</section>
</footer>
</section><!-- #container end -->
<script src="http://www.google.com/jsapi?key=ABQIAAAAr6RY1Z6dchG_sX9WDLSy3xRlq2n1sm52B5HDRR5tm6o8XM18FhR56xHNNH6CsX86uN5VoTrglpyOyQ" type="text/javascript"></script>
<!-- <script src="/js/jquery.js" type="text/javascript"></script> -->
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.2/jquery.min.js"></script>
<script src="/js/jquery-timeago.js" type="text/javascript"></script>
<script src="/js/jquery-easing.js" type="text/javascript"></script>
<script src="/js/jquery-fancybox.js" type="text/javascript"></script>
<script src="/js/jquery-toc.js" type="text/javascript"></script>
<script src="/js/date.js" type="text/javascript"></script>
<script src="/js/feeds.js" type="text/javascript"></script>
<script src="/js/search.js" type="text/javascript"></script>
<script src="/js/hyphenator.min.js" type="text/javascript"></script>
<script src="/js/init.js" type="text/javascript"></script>
<!-- Start Google Analytics -->
<script type="text/javascript">
var _gaq = _gaq || [];
_gaq.push(['_setAccount', 'UA-18587377-1']);
_gaq.push(['_trackPageview']);
(function() {
var ga = document.createElement('script'); ga.type = 'text/javascript'; ga.async = true;
ga.src = ('https:' == document.location.protocol ? 'https://ssl' : 'http://www') + '.google-analytics.com/ga.js';
var s = document.getElementsByTagName('script')[0]; s.parentNode.insertBefore(ga, s);
})();
</script>
<!-- End Google Analytics -->
<!-- Start of StatCounter Code -->
<script type="text/javascript">
var sc_project=6193656;
var sc_invisible=1;
var sc_security="57f7ee2a";
</script>
<script type="text/javascript" src="http://www.statcounter.com/counter/counter_xhtml.js"></script>
<!-- End of StatCounter Code -->
</body>
</html>
|