This starts to sketch common libraries for instantiating informers/listers for a particular GroupVersionResource as one of our duck types.
You can instantiate a duck.InformerFactory like so:
```go
dynaClient, err := dynamic.NewForConfig(cfg)
if err != nil {
logger.Fatalf("Error building dynamic clientset: %v", err)
}
// Cache as the outermost layer so we only register the EventHandler once.
dif := &duck.CachedInformerFactory{
Delegate: &duck.EnqueueInformerFactory{
Delegate: &duck.TypedInformerFactory{
Client: dynaClient,
Type: &duckv1alpha1.Target{},
ResyncPeriod: 30 * time.Second,
StopChannel: stopCh,
},
EventHandler: cache.ResourceEventHandlerFuncs{
AddFunc: func(obj interface{}) {
// Enqueue, obj is: *duckerv1alpha1.Target
},
UpdateFunc: func(old, new interface{}) {
// Enqueue, old and new are: *duckerv1alpha1.Target
},
},
},
}
```
Then, as you come across new GroupVersionResources that you want to handle:
```go
informer, lister, err := dif.Get(gvr)
if err != nil {
logger.Fatalf("Error starting shared index informer: %v", err)
}
```
With the `duck.TypedInformerFactory` the objects will be returned as the provided `Type:`, so in this example, you could safely write:
```go
elt, err := lister.ByNamespace(ns).Get(name)
if err != nil { ... }
target := elt.(*duckv1alpha1.Target)
// Stuff involving target.
```
Matt Moore