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?

score 8 · Accepted Answer · edited Mar 22 '10 at 14:37

8

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()

edited Mar 22 '10 at 14:37

Dónal

answered Mar 21 '10 at 18:39

tim_yates

Thanks a lot Tim! So I have to wait a bit till Groovy 1.7.1 is part of Grails (let's hope in 1.3)... – david Mar 21 '10 at 20:17
1

Just tried it out, and it works in 1.6.3 as well (which I believe is the version of groovy that grails 1.2 uses) :-) – tim_yates Mar 21 '10 at 22:17
1

Yes, this feature was added in Groovy 1.6 http://www.infoq.com/articles/groovy-1-6 – Dónal Mar 22 '10 at 14:36

1 Answers1