Pass param with .& operator to a static method - groovy

Question

With groovy .& operator one can create references to static methods, as in
def static xyz( name='Joe' ) {
println "Hello ${name}"
}
// NOTE: ConsoleScript number part varies
def ref = ConsoleScript52.&xyz
And can be easilly called without params, as
ref() // prints "Hello "
But how can this method be called with params? ref('John') gives an error groovy.lang.MissingMethodException: No signature of method: ConsoleScript52.xyz() is applicable for argument types: (java.lang.String) values: [John]
Note that Groovy does not even use the default value of name param in above example when static method is called with ref.

Answer 1

You are probably using a ConsoleScript instance where you did not define that method with parameters.
In the code below, in the 8th execution in my console (ConsoleScript8) y defined the method hello() without parameters (added the "script number" to make it explicit):
println this.getClass().getName()
println ''
def static hello() {
println "(8) Hello"
}
def h8 = ConsoleScript8.&hello
h8()
h8('Joe')
And it yields the following in the next execution:
ConsoleScript9
(8) Hello
Exception thrown
groovy.lang.MissingMethodException: No signature of method: ConsoleScript9.hello() is applicable for argument types: (java.lang.String) values: [Joe]
And in the 10th execution (ConsoleScript10) I modified it adding the default parameter:
println this.getClass().getName()
println ''
def static hello(name='amigo') {
println "(10) Hello ${name}"
}
def h10 = ConsoleScript10.&hello
h10()
h10('Joe')
println '--'
def h8 = ConsoleScript8.&hello
h8()
h8('Joe')
And it yields:
ConsoleScript12
(10) Hello amigo
(10) Hello Joe
--
(8) Hello
Exception thrown
groovy.lang.MissingMethodException: No signature of method: ConsoleScript8.hello() is applicable for argument types: (java.lang.String) values: [Joe]
It is easier if you use an explicit class:
class Greeter {
def static hello(name='Joe') {
"Hello ${name}"
}
}
def hi = Greeter.&hello
assert hi() == 'Hello Joe'
assert hi('Tom') == 'Hello Tom'

Answer 2

What version of Groovy? This works with Groovy 2.4.5:
class Test {
static greet(name = 'tim') {
"Hello ${name.capitalize()}"
}
}
// regular static calls
assert Test.greet() == 'Hello Tim'
assert Test.greet('kaskelotti') == 'Hello Kaskelotti'
// Create a reference to the static method
def ref = Test.&greet
// Calling the reference works as well
assert ref() == 'Hello Tim'
assert ref('kaskelotti') == 'Hello Kaskelotti'