How can I pass a class to Groovy's Eval binding? - grails

Question

I'm doing some gross stuff, like using Groovy's metaClass and Eval to dynamically assign properties to an object from an XML import:
class ObjectBuilder {
def assignProp(String propName, String propValue) {
Eval.x(this, "x.metaClass.${propName} = '${propValue}'")
}
}
def h = new ObjectBuilder()
h.assignProp('name', 'Henson')
println(h.name)
What I'd like to do though, is be able instantiate another copy of the class inside itself:
Eval.x(this, "x.metaClass.${ObjName} = new ObjectBuilder()")
But I can't, because I think the class isn't passed to the binding. Is there another solution?

Answer 1

A couple of solutions:
Expando
You may try working with a bunch of Expandos:
h = new Expando()
h.last = new Expando()
h.last.name = 'tech'
assert h.last.name == 'tech'
Metaclass the object directly
xml = '''
<person>
<name>john</name>
<surname>doe</surname>
<age>41</age>
<location>St Louis, MO</location>
</person>
'''
class Person {
def name, surname, location, age
}
root = new XmlParser().parseText xml
person = new Person(root.children().collectEntries { [it.name(), it.text()] })
person.metaClass.getFullname = { "$delegate.name $delegate.surname" }
assert person.fullname == "john doe"
person.metaClass.likes = "chicken with lemon"
assert person.likes == "chicken with lemon"
Maps
map = [:]
map.last = [:]
map.last.name = 'Tech'
assert map.last.name == 'Tech'

Answer 2

Passing a newly instantiated object then assigning it with Eval seems to work:
class ObjectBuilder {
def assignProp(String propName, String propValue) {
Eval.x(this, "x.metaClass.${propName} = '${propValue}'")
}
def nestObj(String objName) {
Eval.xy(this, new ObjectBuilder(), "x.metaClass.${objName} = y")
}
}
ObjectBuilder h = new ObjectBuilder()
h.assignProp('name', 'Henson')
h.nestObj('last')
h.last.assignProp('name', 'Tech')
println h.name + ' ' + h.last.name