Passing an instance of a class in Groovy using generics - grails

Question

Grails: 2.4.4
Groovy: 2.4.1
Java : 1.8u40
Windows 7
I am trying to make a generics based controller that members of my team can extend as needed.
Having just getting this issue solved in Groovy with generics ( Why doesn't this generic usage work in groovy?)
I am now running into the following issue in a Grails controller trying to pass an instance of the class.
The TeamCotroller:
class TeamController extends BaseController<Team> {
static allowedMethods = [save: "POST", update: "PUT", delete: "DELETE"]
TeamController() {
super(Team)
}
/*
def index(Integer max) {
params.max = Math.min(max ?: 10, 100)
respond Team.list(params), model:[teamInstanceCount: Team.count()]
}
*/
/*
def show(Team teamInstance) {
respond teamInstance
}
*/
/*
def create() {
respond new Team(params)
}
*/
/* More default CRUD methods cut out for now */
}
The Generic Controller:
class BaseController {
private final Class<T> clazz
BaseController(Class<T> clazz) {
this.clazz = clazz
}
def index(Integer max) {
params.max = Math.min(max ?: 10, 100)
respond clazz.list(params), model:[instanceCount: clazz.count()]
}
// TODO: Figure this out
def show(Team instance) {
respond instance
}
}
In the show(Team instance) method, I have replaced Team with Class<T> and T in an attempt to get the instance being passed to it by Grails/Groovy but it doesn't even seem to be hitting the method at all when I run in debug mode. What does one need to do in order to get the instance being passed to the controller?
--edit-- Adding Exception
2015-03-06 15:56:36,400 [http-bio-8090-exec-5] ERROR errors.GrailsExceptionResolver - MissingPropertyException occurred when processing request: [GET] /test-list/team/show/1
No such property: instance for class: TeamController. Stacktrace follows:
Message: No such property: instance for class: TeamController
-- Edit -- Adding controller code

Answer 1

It doesn't seem to work when passing the instance directly into the parameters of the method, but it does work as expected when using the id parameter, like so:
grails-app/controllers/BaseController.groovy
abstract class BaseController<T> {
private final Class<T> clazz
BaseController() {}
BaseController(Class<T> clazz) {
this.clazz = clazz
}
def index(Integer max) {
params.max = Math.min(max ?: 10, 100)
respond clazz.list(params), model:[instanceCount: clazz.count()]
}
def show(Long id) {
def instance = clazz.get(id)
respond instance
}
}
grails-app/controllers/TeamController.groovy
class TeamController extends BaseController<Team> {
TeamController() {
super(Team)
}
}
Then you should be able to access the /team/show/1.?{format} endpoint without an issue.
I setup an example project here to demonstrate.