问题
When you create a new entity Breeze set id:-1 state:'Added' hasTempKey:true. After export and re-import Breeze doesn't merge the import -1 entity with the current -1 entity in memory it adds a new one... this is explain in the docs... ( but how do we overcome this problem is the question in my case... ) So I tried to set the entity created to setUnchanged(); Now the export import cycle runs as expected but the created entity has lost it's hasTempKey:true property so newly created entity can conflict with a current one... some advice on how to resolve these issues would really be appreciated thanks
回答1:
I assume that this question relates to your approach to implementing a disconnected app as described in this SO question.
As I said there, I you're spending too much time trying to trick Breeze into doing what it should not do. Here, for example, you want EntityManager.saveChanges to not actually save to the remote data store. But the whole point of "saveChanges" is that it persists permanently. "Saving locally" is not really saving. No one but you knows about these saved changes. You don't know if they would pass the business validation rules on your server or if they would collide with a different user's changes. If your laptop dies or is stolen, your locally saved data are gone.
I think breeze can be a huge help in crafting occasionally connected applications. But I think it is critical to properly differentiate stashing changes locally with the intent to save them and actually saving them remotely.
Outline of a Disconnected App
I urge you to take a different tack.
Your app could easily initiate a sequence of distinct editing sessions. For example, one session could be a travel reservation for client 'A', another session for client 'B', and a third session is about something else entirely ... maybe the client 'C' profile.
When your app can't reach the server, it preserves each session as a WIP ("Work In Progress"). Each WIP session its own serialized bundle, identified by a WIP key.
Aside: you'll see this pattern in John Papa's "Building Apps with Angular and Breeze Part 2" when that comes out later this year.
The Breeze EntityManager.exportEntities(list_of_entities) serializes everything about the changed entities of that session including their change-state, original values, and temp keys. Remember that the list_of_entities can be anything including an object graph. You can save that bundle to browser local storage under the WIP key and restore it later.
I'd keep a directory of WIP sessions that included information about the state of the session as a whole (e.g., what kind of editing session it is and whether this session was ready to be persisted remotely). Your app presents WIP sessions to the user while offline. When it gets a connection, it goes through a "synchronization" phase during which it tries to persist the changes. With luck it succeeds. If not, you can rehydrate the session in the UI and help the user reconcile the conflicts.
These are broad strokes. The devil is in the details.
The critical thing in this context is that you do not mess with entity state or the temp keys. You don't care what the keys are or if they change. The serialized session will hold that state information for you. The serialized bundles will move in and out of local storage without complaint. You are using Breeze as intended, while offline or online.
回答2:
The current behavior is deliberate. Generally we assume that temp keys are effectively not comparable. However, I do understand your use case. So, one approach would be to:
1) import your "exported entities" into a temporary EntityManager and check for temp key collisions between this entityManager and your "destination" EntityManager.
2) Then remove any "dups" from the destination EntityManager
3) Import your original "exported entities" into your destination EntityManager
You can actually skip step 1 if you know that all tempKeys are dups.
Another approach would be to use Guid's for your keys. This completely bypasses the temp key issue because Guid never need to be "temporary".
来源：https://stackoverflow.com/questions/19557318/exporting-importing-breeze-model-and-hastempkey-issues