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<p><table class="wysiwyg-macro" data-macro-name="excerpt" data-macro-parameters="atlassian-macro-output-type=BLOCK|hidden=true" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2V4Y2VycHQ6aGlkZGVuPXRydWV8YXRsYXNzaWFuLW1hY3JvLW91dHB1dC10eXBlPUJMT0NLfQ&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="RICH_TEXT"><tr><td class="wysiwyg-macro-body"><p>Dynamically creating method names</p></td></tr></table></p>

<h1>ExpandoMetaClass - Dynamic method/property name creation</h1>

<p>Since Groovy allows you to use Strings as property names this in turns allows you to dynamically create method and property names at runtime.</p>

<h3>The Basics</h3>

<p>To create a method with a dynamic name simply use Groovy's feature of reference property names as strings. You can combine this with Groovy's string interpolation (Gstrings) to create method and property names on the fly:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
class Person {
   String name = "Fred"
}

def methodName = "Bob"

Person.metaClass."changeNameTo${methodName}" = {-> delegate.name = "Bob" }

def p = new Person()

assert "Fred" == p.name

p.changeNameToBob()

assert "Bob" == p.name
</pre></td></tr></table>
<p>The same concept can be applied to static methods and properties.</p>

<h3>A more elaborate example</h3>

<p>In Grails we have a concept of dynamic codecs, classes that can encode and decode data.</p>

<p>These classes are called HTMLCodec, JavaScriptCodec etc. an example of which can be seen below:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
import org.springframework.web.util.HtmlUtils
class HTMLCodec {
    static encode = { theTarget ->
        HtmlUtils.htmlEscape(theTarget.toString())
    }

static decode = { theTarget ->
    	HtmlUtils.htmlUnescape(theTarget.toString())
    }
}
</pre></td></tr></table>
<p>So what we do with these classes is to evaluate the convention and add &quot;encodeAsXXX&quot; methods to every object based on the first part of the name of the codec class such as &quot;encodeAsHTML&quot;. The pseudo code to achieve this is below:</p>
<table class="wysiwyg-macro" data-macro-name="code" style="background-image: url(/plugins/servlet/confluence/placeholder/macro-heading?definition=e2NvZGV9&amp;locale=en_GB&amp;version=2); background-repeat: no-repeat;" data-macro-body-type="PLAIN_TEXT"><tr><td class="wysiwyg-macro-body"><pre>
def codecs = classes.findAll { it.name.endsWith('Codec') }

codecs.each { codec ->
    Object.metaClass."encodeAs${codec.name-'Codec'}" = { codec.newInstance().encode(delegate) }
    Object.metaClass."decodeFrom${codec.name-'Codec'}" = { codec.newInstance().decode(delegate) }
}

def html = '&lt;html>&lt;body>hello&lt;/body>&lt;/html>'

assert '&amp;lt;html&amp;gt;&amp;lt;body&amp;gt;hello&amp;lt;/body&amp;gt;&amp;lt;/html&amp;gt;' == html.encodeAsHTML()
</pre></td></tr></table>
<p>As you can see from the above we dynamically construct the names of the methods using GString expressions!</p>