On closures and groovy builder pattern -

starting grasp closures in general , groovy features.

given following code:

class mailer {     void to(final string to) { println "to $to" }     void from(final string from) { println "from $from" }      static void send(closure configuration) {         mailer mailer = new mailer()         mailer.with configuration     }   }  class mailsender {     static void sendmessage() {         mailer.send {             'them'             'me'         }     } }  mailsender.sendmessage() 

what happens under hood when pass closure mailer.send method?

does to , from passed arguments closure point of view? types closure maps them?

and inside mailer.send method @ moment mailer object calls mailer.with receiving configuration object, object maps them method calls. groovy reflection?

groovy can dynamically define delegate of closure , this object.

with setting delegate , executing closure. verbose way achieve same:

def math = {     given 4     sum 5     print }   class printmath {     def initial     def given(val) {         initial = val     }      def sum(val) {         initial += val     }      def getprint() {         println initial         return initial     } }  math.delegate = new printmath() math.resolvestrategy = closure.delegate_only  assert math() == 9 

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what happens under hood when pass closure mailer.send method?

it receives not-yet-executed block of code.

does , passed arguments closure point of view?

no, better thinking of them anonymous class/lambda in java, or function(){} in javascript.

which types closure maps them?

none, method calls waiting executed. can delegated different objects, though.

and inside mailer.send method @ moment mailer object calls mailer.with receiving configuration object, object maps them method calls. groovy reflection?

you can decompile groovy class file see going on. iirc, groovy uses "reflector" strategy (with arrayofcallsite caching) make calls faster or can use invokedynamic.

the closure math in code above result in class:

// .. lot of techno-babble  public object docall(object it) {     callsite[] arrayofcallsite = $getcallsitearray();     arrayofcallsite[0].callcurrent(this, integer.valueof(4));     arrayofcallsite[1].callcurrent(this, integer.valueof(5));     return arrayofcallsite[2].callgroovyobjectgetproperty(this);     return null; }