Groovy meta-programming - adding static methods to Object.metaClass

Question

I've encountered a Groovy meta-programming problem which I'm unable to solve.

When adding the static method foo() to the class FooBar, then FooBar.foo() works as expected:

FooBar.metaClass.static.foo = {
    println "hello"
}
FooBar.foo()

However, I instead add the same static method foo() to the class Object, then FooBar.foo() fails with an MissingMethodException:

Object.metaClass.static.foo = {
    println "hello"
}
FooBar.foo()
// groovy.lang.MissingMethodException:
// No signature of method: FooBar.foo() is applicable for argument types: 
// () values: []

Why is that? Shouldn't Object.metaClass.static.foo = { .. } add foo() also to FooBar?

Answer 1

In order to get the behavior you're looking for you need to call ExpandoMetaClass.enableGlobally()

Keep in mind doing this has a bigger memory footprint than normal meta-programming.

http://groovy.codehaus.org/api/groovy/lang/ExpandoMetaClass.html#enableGlobally()