(Quick Reference)
                instanceOf
Purpose
Determines if a domain class instance is an instance of the specified class, resolving the actual class if the instance is a proxy.
Examples
Given the domain classes:
class Container {
   static hasMany = [children: Child]
}class Child {
   String name
   static belongsTo = [container: Container]
}class Thing extends Child {}class Other extends Child {}Then you can determine the type of the elements in a 
Container's 
children collection using
def container = Container.get(id)
for (child in container.children) {
   if (child.instanceOf(Thing)) {
      // process Thing
   }
   else if (child.instanceOf(Other)) {
      // process Other
   }
   else {
      // handle unexpected type
   }
}Description
Parameters:
- clazz- the type to check