all repos — h3rald @ 9504a69adcee918506f2e81007520b76e07505bc

The sources of https://h3rald.com

content/glyph/book/extending/placeholders.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
 
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">
<html xmlns="http://www.w3.org/1999/xhtml" xml:lang="en">
	<head>
		<title>Glyph - Using Placeholders</title>
		<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, technical writing, html, html5, book" />
		<link rel="shortcut icon" href="/favicon.ico" type="image/x-icon" />
		<meta http-equiv="content-type" content="text/html; charset=UTF-8" />
		<meta content="44.388041;9.073248" name="ICBM" />

		<link href="/css/main.css" media="all" rel="stylesheet" type="text/css" />
	</head>
	<body>
		<div id="wrapper">
			<a href="http://github.com/h3rald/h3rald"><img style="position: absolute; top: 0; right: 0; border: 0;" src="http://s3.amazonaws.com/github/ribbons/forkme_right_red_aa0000.png" alt="Fork me on GitHub" /></a>
			<div id="header">
				<!--[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 &ndash; and <em>safer</em> &ndash; web experience. [<a href="http://browsehappy.com/browsers/">Read More...</a>]
				</div>
				<![endif]-->
				<!-- HEADER START -->
				<div id="header-container">
					<div id="header-left">
						<h1><span class="logo"></span><a id="logo" href="/" title="H3RALD"></a></h1>
					</div>
					<div id="header-right">
						<ul id="navigation">
							<li><span class="preload nav-archives"></span><a id="nav-archives" href="/archives/" title="ARCHIVES"></a></li>
							<li><span class="preload nav-projects"></span><a id="nav-projects" href="/projects/" title="PROJECTS"></a></li>
							<li><span class="preload nav-about"></span><a id="nav-about" href="/about/" title="ABOUT"></a></li>
							<li><span class="preload nav-other"></span><a id="nav-other" href="/other/" title="OTHER"></a></li>
						</ul>
					</div>
				</div>
			</div>
			<!-- HEADER END -->
			<div class="ribbon">
			</div>
			<!-- MAIN START -->
			<div id="main">
				<!-- CONTAINER START -->
				<div id="container">
					<!-- CONTENT START -->
					<div id="content" class="clearfixstandard">
						<div id="page-links">
							<span><script type="text/javascript" src="http://w.sharethis.com/button/sharethis.js#publisher=6e34d60c-b14e-4c19-9b2f-7c35a9f0ab09&amp;type=website&amp;linkfg=%23a4282d"></script></span>
						</div>

						<h2>Using Placeholders</h2>
						<hr />
						<div id="content-body">
							<div class="navigation"><a href="/glyph/book/extending/bookmarks_headers.html">Bookmarks and Headers &larr;</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/extending/validators.html">&rarr; Using Validators</a></div>
								<p>Sometimes you may need to access some data that will not be available until the entire document has been fully parsed and analyzed. For example, in order to be able to validate internal links, it is necessary to know in advance if the bookmark ID referenced in the link exists or not, either before (that&#8217;s easy) or even <em>after</em> the link.</p>
<p>Here&#8217;s the source code of the <a href="/glyph/book/macros/macros_inline.html#m_link"><code>link</code></a> macro:</p>
	<pre class="lazy"><span class="line-numbers">   1 </span> macro <span class="Constant"><span class="Constant">:</span>link</span> <span class="Keyword">do</span>
<span class="line-numbers">   2 </span>   href, title <span class="Keyword">=</span> <span class="Variable"><span class="Variable">@</span>params</span>
<span class="line-numbers">   3 </span>   <span class="Keyword">if</span> href.<span class="Entity">match</span> <span class="String"><span class="String">/</span></span><span class="String">^#</span><span class="String"><span class="String">/</span></span> <span class="Keyword">then</span>
<span class="line-numbers">   4 </span>     anc <span class="Keyword">=</span> href.<span class="Entity">gsub</span>(<span class="String"><span class="String">/</span></span><span class="String">^#</span><span class="String"><span class="String">/</span></span>, <span class="String"><span class="String">'</span><span class="String">'</span></span>).<span class="Entity">to_sym</span>
<span class="line-numbers">   5 </span>     bmk <span class="Keyword">=</span> bookmark? anc
<span class="line-numbers">   6 </span>     <span class="Keyword">if</span> bmk <span class="Keyword">then</span>
<span class="line-numbers">   7 </span>       title <span class="Keyword">||=</span> bmk[<span class="Constant"><span class="Constant">:</span>title</span>]
<span class="line-numbers">   8 </span>     <span class="Keyword">else</span>
<span class="line-numbers">   9 </span>       plac <span class="Keyword">=</span> placeholder <span class="Keyword">do </span>|<span class="Variable">document</span>|
<span class="line-numbers">  10 </span>         macro_error <span class="String"><span class="String">&quot;</span>Bookmark '<span class="String"><span class="String">#{</span>anc<span class="String">}</span></span>' does not exist<span class="String">&quot;</span></span> <span class="Keyword">unless</span> document.<span class="Entity">bookmarks</span>[anc] 
<span class="line-numbers">  11 </span>         document.<span class="Entity">bookmarks</span>[anc][<span class="Constant"><span class="Constant">:</span>title</span>]
<span class="line-numbers">  12 </span>       <span class="Keyword">end</span>
<span class="line-numbers">  13 </span>       title <span class="Keyword">||=</span> plac
<span class="line-numbers">  14 </span>     <span class="Keyword">end</span>
<span class="line-numbers">  15 </span>   <span class="Keyword">end</span>
<span class="line-numbers">  16 </span>   title <span class="Keyword">||=</span> href
<span class="line-numbers">  17 </span>   <span class="String"><span class="String">%{</span>&lt;a href=&quot;<span class="String"><span class="String">#{</span>href<span class="String">}</span></span>&quot;&gt;<span class="String"><span class="String">#{</span>title<span class="String">}</span></span>&lt;/a&gt;<span class="String">}</span></span>
<span class="line-numbers">  18 </span> <span class="Keyword">end</span>
</pre>
	<p>If there&#8217;s already a bookmark stored in the current document, then it is possible to retrieve its title and use it as link text. Otherwise, it is necessary to wait until the entire document has been fully processed and then check if the bookmark exists. To do so, use the <code>placeholder</code> method. When called, this method returns an unique placeholder, which is then substituted with the value of the block, right before the document is finalized.</p>
<p>Within the <code>placeholder</code> block, the <code>document</code> parameter is, by all means, the fully analyzed document.</p>
							<div class="navigation"><a href="/glyph/book/extending/bookmarks_headers.html">Bookmarks and Headers &larr;</a><a href="/glyph/book/index.html">Contents</a><a href="/glyph/book/extending/validators.html">&rarr; Using Validators</a></div>
						</div>
						<div id="content-footer">
							<div class="share">
								<script type="text/javascript"><!--
									google_ad_client = "pub-2871497824158668";
									/* 728x90, h3rald 8.0 */
									google_ad_slot = "0081634732";
									google_ad_width = 728;
									google_ad_height = 90;
									//-->
									</script>
									<script type="text/javascript"
										src="http://pagead2.googlesyndication.com/pagead/show_ads.js">
										</script>
									</div>
								</div>
							</div>
							<!-- CONTENT END -->
						</div>
						<!-- CONTAINER END -->
					</div>
					<div class="ribbon"></div>
					<!-- MAIN END -->
					<div id="border-bottom">
						<div id="services">
							<div class ="footer-left">
								<div id="backtype">
									<h3><span class="s-opinions preload"></span><a id="s-opinions" href="http://www.backtype.com/h3rald" title="Opinions"></a></h3>
								</div>
							</div>
							<div class ="footer-center">
								<div id="twitter">
									<h3><span class="s-tweets preload"></span><a id="s-tweets" href="http://www.twitter.com/h3rald" title="Tweets"></a></h3>
								</div>
							</div>
							<div class ="footer-right">
								<div id="delicious">
									<h3><span class="s-bookmarks preload"></span><a id="s-bookmarks" href="http://www.delicious.com/h3rald" title="Bookmarks"></a></h3>
								</div>
							</div>
						</div> <!-- SERVICES END -->
					</div>
					<div class="clearfooter"></div>
				</div> <!-- WRAPPER END -->
				<div id="footer">
					<div id="footer-container">
						<div class="footer-div">
							H3RALD Web Site v8.0.0 <em>"xStatic"</em> &mdash; &copy; 2004-2010 <strong>Fabio Cevasco</strong> &mdash; <a class="link" href="http://creativecommons.org/licenses/by-nc-nd/3.0/us/">Some rights reserved</a> | <a href="http://validator.w3.org/check?uri=referer" class="link">XHTML 1.1</a> | <a href="http://jigsaw.w3.org/css-validator/validator?uri=/t_34.html" class="link">CSS 2.1</a>
						</div>
					</div> <!-- END FOOTER CONTAINER-->
				</div> <!-- END FOOTER -->
				<!-- 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 -->
				<script src='http://www.google-analytics.com/ga.js' type='text/javascript'></script>	
				<script src="http://www.google.com/jsapi?key=ABQIAAAA6h3j8Jri5D_da53UPbEbThRlq2n1sm52B5HDRR5tm6o8XM18FhTKn3v155RpPeD0kWnWG81QEhhifQ" type="text/javascript"></script>
				<script src="http://www.google.com/jsapi?key=ABQIAAAA6h3j8Jri5D_da53UPbEbThRlq2n1sm52B5HDRR5tm6o8XM18FhTKn3v155RpPeD0kWnWG81QEhhifQ" type="text/javascript"></script>
					<script src="/js/jquery.js" type="text/javascript"></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/init.js" type="text/javascript"></script> 
				
				
					<script type="text/javascript"> 
						$(document).ready(function() {
								display_opinions(7);
								display_tweets(7);
								display_bookmarks(7);
								});
					</script> 
			</body>
		</html>