Pass param with .& operator to a static method

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'