GXT 3 dynamically update an element in a treeStore - gwt

Question

i'm currently using GXT 3 to display elements in a Tree.
These elements are retrieved from database and identified in the Tree by their id (by that, I mean that the id is the ModelKeyProvider of my store).
I also made it possible for users to create objects locally in the tree with the following code:
private Tree<EntityDAO, String> tree;
private TreeStore<EntityDAO> store;
int count = 1;
// instanciation and irrelevant stuff
...
EntityDAO sel = tree.getSelectionModel().getSelectedItem();
EntityDAO child = new EntityDAO();
child.setId((long) count);
store.add(store.getParent(sel), child);
count++;
tree.setExpanded(sel, true);
tree.getSelectionModel().select(child, false);
As you can see, i set a temporary id (count) to my local object.
The issue occurs when I save my object in database. A permanent id is then set to my EntityDAO but when i try to set this id to my local object to sync it with the database, it doesn't work.
I've tried to modify the child id directly
child.setId(result);
tree.update(child);
I've tried to add a copy of my object with the proper id, and then to remove my object from the tree
EntityDAO newPR = child;
newPR.setId(result);
store.add(store.getParent(child), newPR);
store.remove(child);
But the display is never updated. Any clue?

Answer 1

Let's discuss about the first way you tried, the update method:
child.setId(result);
tree.update(child);
From the update method API state this :
Replaces the item that matches the key of the given item, and fires a
StoreUpdateEvent to indicate that this change has occurred. Any
changes to the previous model via it's record instance will be lost
and the record will be removed. This will not cause the sort or filter
to be re-applied to the object. Overrides: update(...) in Store
Parameters: item the new item to take its place in the Store.
So basically, the update method will replace the item inside the store that have the same key with your parameter. Your data have a new key that doesn't exist inside the store, that's why it doesn't effected anything to your tree display.
Second, let's discuss the create a copy of your object and set it with the proper id:
EntityDAO newPR = child;
newPR.setId(result);
store.add(store.getParent(child), newPR);
store.remove(child);
This way actually will work, but you only have one small problem. The first line of your code actually just give you a variable that have a reference to your old object (the child object), so whenever you remove the child, the newPR also removed. You should really create a new object using the constructor, here how I think you should do it:
EntityDAO newPR = new EntityDAO();
newPR.setId(result);
newPR.setOtherProperty(child.getOtherProperty());
// just copy all property of child to newPR
store.add(store.getParent(child), newPR);
store.remove(child);
Hope this can help you.