Question

I’m working on a grails application atm. I need a property on an abstract java class (org.quartz.Trigger) adding

Trigger.metaClass.id = { delegate.hashCode() }

before I call the class works. I would like to enable this for all my Triggers in my application. Is this possible? Or do I have to repeat this everytime I need the property?

Answer 1

If you add to the metaClass before any Trigger objects are instantiated, then this addition will exist in all of them.

However, after they are created, you would need to add it to every instance of Trigger.

Of course, this method will only be visible from Groovy, as Java does not know about the metaClass.

Some example Groovy code showing this in action:

// Add to the metaClass of an anstract java class
AbstractList.metaClass.woo = { 'hi there' }

// Create an instance of a class that extends this abstract class
ArrayList list = [ 1, 2, 3 ]

// Call the closure in the metaClass
println list.woo()