I'm using GWT 2.4 with RequestFactory but not still everything is clear for me.
In this article author wrote about situation when we used an entity proxy with one instance of RequestContext and want to reuse (edit()) this entity proxy with other instance of RequestContext:
It cannot be edited because it has already a requestContext assigned. If you want to change it you must retrieve instance of this entity from server again
But I'm getting no exceptions when I execute this code:
RequestContext newRequest1 = factory.myRequest();
newRequest1.edit(proxy);
RequestContext newRequest2 = factory.myRequest();
newRequest2.edit(proxy);
The problems (exception) described by autor pop up when I run this version:
RequestContext newRequest1 = factory.myRequest();
MyProxy edited = newRequest1.edit(proxy);
RequestContext newRequest2 = factory.myRequest();
newRequest2.edit(edited);
So it seems that only editable copy returned by edit() is directly related with RequestContext instance.
In that case is there something wrong in approoach in which I keep one instance of (uneditable/frozen) proxy in my edit view and each time user clicks "edit" button I edit() it with new fresh RequestContext? Or should I obtain fresh instance of proxy each time too?
Getting new instance of proxy seems a bit awkward for me but I guess reusing one proxy instance may cause some issues related to sending delta of changes to server?
So to rephrase the question: it a good practice to reuse single instance of proxy with multiple RequestContexts?
There's no problem editing the same proxy twice (or more), as long as there's only a single editable instance at a time (your first code snippet should throw; if it's not then it's a bug; it could work if you don't keep references on both the RequestContext and the edited proxy).
Note that RequestFactory sends only the modified properties to the server, but it does so by diff'ing with the non-editable instance passed to edit(); so you should try to use the most recent instance as possible to keep your server-side/persisted data as close to your client-side data as possible (could seem obvious, but can lead to some surprises in practice: if you see foo on the client but have bar on the server, you'll keep the bar on the server-side until you modify the property on the client-side to something other than foo)