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


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"

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"
// 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?

Best Solution

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.


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