Programming Groovy 2

14.3 Synthesizing Methods for Specific Instances

We saw how to inject methods into specific instances of a class in Section 13.3, ​Injecting Methods into Specific Instances​. We can dynamically synthesize methods into specific instances, as well, by providing the instance(s) with a specialized ​MetaClass​. Here is an example:

class Person {}

def emc = new ExpandoMetaClass(Person)
emc.methodMissing = { String name, args ->
  "I'm Jack of all trades... I can $name"
}
emc.initialize()

def jack = new Person()
def paul = new Person()

jack.metaClass = emc

println jack.sing()
println jack.dance()
println jack.juggle()

try {
  paul.sing()
} catch(ex) ...