About
The Expando class can be used to create a dynamically object that can be extended with properties (or methods) at runtime.
def expando = new Expando()
expando.name = 'John'
assert expando.name == 'John'
A special case occurs when a dynamic property registers a Closure code block. Once being registered it can be invoked as it would be done with a method call.
def expando = new Expando()
expando.toString = { -> 'John' }
expando.say = { String s -> "John says: ${s}" }
assert expando as String == 'John'
assert expando.say('Hi') == 'John says: Hi'