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| Code Block |
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class Person {
String name = "Fred"
}
def methodName = "Bob"
Person.metaClass."changeNameTo${methodName}" = {-> delegate.name = "Bob" }
def p = new Person()
assert "Fred" == p.name
p.changeNameToBob()
assert "Bob" == p.name
|
The
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same
...
concept
...
can
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be
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applied
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to
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static
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methods
...
and
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properties.
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A more elaborate example
In Grails we have a concept of dynamic codecs, classes that can encode and decode data.
...
| Code Block |
|---|
import org.springframework.web.util.HtmlUtils
class HTMLCodec {
static encode = { theTarget ->
HtmlUtils.htmlEscape(theTarget.toString())
}
static decode = { theTarget ->
HtmlUtils.htmlUnescape(theTarget.toString())
}
}
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So what we do with these classes is to evaluate the convention and add "encodeAsXXX" methods to every object based on the first part of the name of the codec class such as "encodeAsHTML". The pseudo code to achieve this is below:
| Code Block |
|---|
def codecs = classes.findAll { it.name.endsWith('Codec') }
codecs.each { codec ->
Object.metaClass."encodeAs${codec.name-'Codec'}" = { codec.newInstance().encode(delegate) }
Object.metaClass."decodeFrom${codec.name-'Codec'}" = { codec.newInstance().decode(delegate) }
}
def html = '<html><body>hello</body></html>'
assert '<html><body>hello</body></html>' == html.encodeAsHTML()
|
...