Mercurial > lua-expat / file revision

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Strict//EN"
   "http://www.w3.org/TR/xhtml1/DTD/xhtml1-strict.dtd">
<html>
<head>
	<title>LuaExpat: XML Expat parsing for the Lua programming language</title>
    <link rel="stylesheet" href="../doc.css" type="text/css"/>
	<meta http-equiv="Content-Type" content="text/html; charset=UTF-8"/>
</head>
<body>

<div id="container">

<div id="product">
	<div id="product_logo"><a href="http://www.keplerproject.org">
        <img alt="LuaExpat logo" src="luaexpat.png"/>
	</a></div>
	<div id="product_name"><big><strong>LuaExpat</strong></big></div>
	<div id="product_description">XML Expat parsing for the Lua programming language</div>
</div> <!-- id="product" -->

<div id="main">

<div id="navigation">
<h1>LuaExpat</h1>
	<ul>
		<li><a href="index.html">Home</a>
			<ul>
				<li><a href="index.html#overview">Overview</a></li>
				<li><a href="index.html#status">Status</a></li>
				<li><a href="index.html#download">Download</a></li>
				<li><a href="index.html#history">History</a></li>
				<li><a href="index.html#references">References</a></li>
				<li><a href="index.html#credits">Credits</a></li>
				<li><a href="index.html#contact">Contact</a></li>
			</ul>
		</li>
		<li><a href="manual.html">Manual</a>
			<ul>
				<li><a href="manual.html#introduction">Introduction</a></li>
				<li><a href="manual.html#installation">Installation</a></li>
				<li><a href="manual.html#parser">Parser Objects</a></li>
			</ul>
		</li>
		<li><strong>Examples</strong></li>
		<li><a href="lom.html">Lua Object Model</a></li>
        <li><a href="http://luaforge.net/projects/luaexpat/">Project</a>
            <ul>
                <li><a href="http://luaforge.net/tracker/?group_id=13">Bug Tracker</a></li>
                <li><a href="http://luaforge.net/scm/?group_id=13">CVS</a></li>
            </ul>
        </li>
		<li><a href="license.html">License</a></li>
	</ul>
</div> <!-- id="navigation" -->

<div id="content">

<h2><a name="examples"></a>Examples</h2>

<p>The code excerpt below creates a parser with 2 callbacks and
feeds a test string to it. The parsing of the test string triggers
the callbacks, printing the results.</p>

<pre class="example">
require"lxp"

local count = 0
callbacks = {
    StartElement = function (parser, name)
        io.write("+ ", string.rep(" ", count), name, "\n")
        count = count + 1
    end,
    EndElement = function (parser, name)
        count = count - 1
        io.write("- ", string.rep(" ", count), name, "\n")
    end
}

p = lxp.new(callbacks)

for l in io.lines() do  -- iterate lines
    p:parse(l)          -- parses the line
    p:parse("\n")       -- parses the end of line
end
p:parse()               -- finishes the document
p:close()               -- closes the parser
</pre>

<p>For a test string like</p>

<pre class="example">
&lt;elem1&gt;
    text
    &lt;elem2/&gt;
    more text
&lt;/elem1&gt;
</pre>

<p>The example would print</p>

<pre class="example">
+ elem1
    + elem2
    - elem2
- elem1
</pre>

<p>Note that the text parts are not handled since the corresponding
callback (<em>CharacterData</em>) has not been defined. Also note
that defining this callback after the call to lxp.new would make no
difference. But had the callback table been defined as</p>

<pre class="example">
callbacks = {
    StartElement = function (parser, name)
        io.write("+ ", string.rep(" ", count), name, "\n")
        count = count + 1
    end,
    EndElement = function (parser, name)
        count = count - 1
        io.write("- ", string.rep(" ", count), name, "\n")
    end,
    CharacterData = function (parser, string)
        io.write("* ", string.rep(" ", count), string, "\n")
    end
}
</pre>

<p>The results would have been</p>

<pre class="example">
+ elem1
* text
    + elem2
    - elem2
* more text
- elem1
</pre>

<p>Another example would be the use of <em>false</em> as a
placeholder for the callback. Suppose that we would like to print
only the text associated with <em>elem2</em> elements and that the
XML sample is</p>

<pre class="example">
 &lt;elem1&gt;
    text
    &lt;elem2&gt;
        inside text
    &lt;/elem2&gt;
    more text
&lt;/elem1&gt;
</pre>

<p>We could define the new callback table as</p>

<pre class="example">
callbacks = {
    StartElement = function (parser, name)
      if name == "elem2" then
        -- redefines CharacterData behaviour
        callbacks.CharacterData = function (parser, string)
          io.write(string, "\n")
        end
      end
    end,

    EndElement = function (parser, name)
      if name == "elem2" then
        callbacks.CharacterData = false -- restores placeholder
      end
    end,

    CharacterData = false               -- placeholder
}
</pre>

<p>The results would have been</p>

<pre class="example">
inside text
</pre>

<p>Note that this example assumes no other elements are present
inside elem2 tags.</p>

</div> <!-- id="content" -->

</div> <!-- id="main" -->

</div> <!-- id="container" -->

</body>
</html>