Using FEMMapping as NSMapTable key leads to duplicated objects

[jcavar]

Hi,
It new version, FEM uses FEMMapping instead entity name as before as NSMapTable key. When using recursive relationships and therefore different FEMMapping in child object and when processing child, it tries to get object from cache but since child mapping is different it can't get it and inserts new object.

Simple solution is I think just to use mapping.entityName as key.

[dimazen]

Can you share code of the mapping that you're using as well as some sample JSON, please?

[dimazen]

Side note about why I rewrote code to use FEMMapping as a key instead of entityName and why we can't go back: initially I was planning to use the same prefetch code for the Realm extension. However later it turned out that no prefetch required for the Realm. So why I didn't move the code back? In the next version I'm planning to deprecate entityName, and to leave simply objectClass for all of the cases. Using class instead of the entityName gives me ability to cache setter implementations and to speed up deserialization.

[jcavar]

Here is simplified version:

Chat:

+ (FEMMapping *)recursiveMapping {
    FEMMapping *mapping = [[FEMMapping alloc] initWithEntityName:@"WCTChat"];
    [mapping addAttribute:[WCTChat identifierAttribute]];
    mapping.primaryKey = @"identifier";
    return mapping;
}

+ (FEMMapping *)defaultMapping {
    FEMMapping *mapping = [[FEMMapping alloc] initWithEntityName:@"WCTChat"];
    [mapping addAttribute:[WCTChat identifierAttribute]];
    [mapping addRelationshipMapping:[WCTMessage defaultMapping]
                        forProperty:@"lastMessage"
                            keyPath:@"lastMsg"];
    mapping.primaryKey = @"identifier";
    return mapping;
}

Message:

+ (FEMMapping *)defaultMapping {
    FEMMapping *mapping = [[FEMMapping alloc] initWithEntityName:@"WCTMessage"];
    [mapping addRelationshipMapping:[WCTChat recursiveMapping]
                        forProperty:@"chat"
                            keyPath:@"chat"];
    mapping.primaryKey = @"identifier";
    return mapping;
}

JSON:

"chat" : {
    "idChat" : 1,
    "lastMsg" : {
        "chat" : { idChat" : 1 },
        "idMessage" : 345
    }
}

[jcavar]

Sure, objectClass should be fine as well.

[jcavar]

And also, I know that we can't do much about it now, but I think it would be much nicer if there was bug fixes release before Realm support. We wanted to get temporary fix for #80 but had to include whole Realm support as well, which in the end it seems broke some of functionality.

[dimazen]

Agree, that to rollout a bugfix release would be a better option. Anyway it is a little bit late.

[dimazen]

I'll try to release a hotfix within 1.5 hours

[dimazen]

Observation: @jcavar do you have an inverse relationship? It looks like that you're trying to map chat to the message that is already included into the chat property.

[dimazen]

@jcavar this issue has been fixed in the 1.2.1 release.
Available in both Carthage and Pods (don't forget to update your repo)!

[jcavar]

@dimazen thank you, that was fast 👍

Yes, we have inverse relationship from message to chat.

[dimazen]

@jcavar what I meant by my observation is that you probably don't need nested Chat mapping, since Message already included into the Chat and by using inverse relationship CoreData will be able to set a correct chat value on the message object.

In any case thanks for your report!

[jcavar]

Yes, that is good point, but we have explicitly disabled inverse relationship in CoreData editor for some reason.

[dimazen]

Got it. Good luck with your project 👍