Groovy: add a method to a closure

Question

I have the following closure

def closure = {
   println ("closure code")
}

And i would like to add a method to it. but if I try

 closure.metaClass.fun = { c->
        c.call();
        println ("extra code");
 }   

I get an Exception

groovy.lang.MissingPropertyException: No such property: fun for class: org.codehaus.groovy.runtime.metaclass.ClosureMetaClass

Reading another answer, i also blindly tried to call

ExpandoMetaClass.enableGlobally()

but it's not working.

Is there a way to achive what I want?

Answer 1

You can do:

def closure = {
    println "closure code"
}

closure.getMetaClass().fun = { ->
    delegate.call()
    println "extra code"
}   

closure.fun()

Which prints:

closure code
extra code

Answer 2

Another simpler approach could be:

def closure = {    
    println "closure code" 
}  

closure.fun = { ->  
    closure()
    println "extra code" 
}     

closure.fun()

The downside of this approach is that I'm referencing the closure variable directly though, instead of going through the delegate.