Groovy Mixin on Instance (Dynamic Mixin)

Question

I'm trying to achieve following:

class A {
  def foo() { "foo" }
}

class B {
  def bar() { "bar" }
}

A.mixin B
def a = new A()

a.foo() + a.bar()

with one significant difference - I would like to do the mixin on the instance:

a.mixin B

but this results in

groovy.lang.MissingMethodException: No signature of method: A.mixin() is applicable for argument types: (java.lang.Class) values: [class B]

Is there a way to get this working like proposed in the Groovy Mixins JSR?

Answer 1

You can do this since Groovy 1.6

Call mixin on the instance metaClass like so:

class A {
  def foo() { "foo" }
}

class B {
  def bar() { "bar" }
}

def a = new A()
a.metaClass.mixin B

a.foo() + a.bar()