Calling void methods is fine. Expecting a result is the point in question.

For dynamic Groovy, you can't always tell which case you have:

class Foo {
  def bar() { 42 }
  void baz() { }

def method(boolean condition, delegate, meth1, meth2) {
  if (condition) delegate."$meth1"()
  else delegate."$meth2"()

println method(true, new Foo(), 'bar', 'baz') // 42
println method(false, new Foo(), 'bar', 'baz') // null

Here, "method" is expecting to return some value that happens to be the last expression, i.e. the result of the if/then/else expression, so we return null in such cases.

Cheers, Paul.

On Tue, Sep 4, 2018 at 7:38 AM MG <> wrote:
What I meant was: What sense does letting void methods be called make
for the dynamic case, i.e. the dynamic compiler ? From a programmer's
perspective, i.e. what is a programming use case for that
feature/behavior, in dynamic Groovy ?

Of course I can do the following in dynamic Groovy:

// Groovy 2.5.0
class Goo {
     //void nogoo() { return 123 } // Dynamic Groovy compiler: RuntimeParserException: Cannot use return statement with an expression on a method that returns void
     void nogoo() { 123 }

final goo = new Goo()

println "original: goo.nogoo()=${goo.nogoo()}"

goo.metaClass.nogoo = { return 456 }

println "mopped: goo.nogoo()=${goo.nogoo()}"

Which will build, run, and output

original: goo.nogoo()=null
mopped: goo.nogoo()=456

  i.e. returning 456 from a void method in the second case.
But if I am using a library that includes the Goo class, why would I
ever expect a return value from the nogoo method (and therefore call
it), considering its return type is void ? And if I control the Goo
class myself, why would I not just change its return type to int or def ?


On 03.09.2018 22:36, Jochen Theodorou wrote:
> On 03.09.2018 17:13, mg wrote:
>> But in what scenario does the dynamic behavior make sense ?
> for a static compiler? none other than being compatible
> bye Jochen