Question: Is it possible to addConnectionForRelationship: with a abstract entity relationship and connectedBy: with a child entity's attributeName?

[puttin]

Example:
Article have a author relationship which point to PenName entity.
PenName have a people relationship which point to People abstract entity.
People has two child entity: Boy and Girl.
Boy have a boyID, Girl have a girlID.

Here comes a JSON:

{
    "articleID": 1,
    "boy_pen_name": {
        "11": @"Jack"
    }
}

"11" is the boyID.
"Jack" is the pen name

I can use RKDynamicMapping to ensure "boy_pen_name" is mapping with a boy PenName mapping.
But how to addConnectionForRelationship:connectedBy: for the people relationship of PenName?
Because People abstract entity don't have any ID attribute.

---

I came up with a workaround:

The workaround is NOT working:

+ [PenName boyPenNameMapping]:
…
mapping.identificationAttributes = @[@"peopleID", @"penName"];
[mapping addAttributeMappingFromKeyOfRepresentationToAttribute:@"peopleID"];
[mapping addAttributeMappingsFromDictionary:@{@"{peopleID}": @"penName"}];
[mapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:nil toKeyPath:@"people" withMapping:[Boy magicMapping]]];
…

+ [Boy magicMapping]:
…
mapping.identificationAttributes = @[@"boyID"];
[mapping addAttributeMappingFromKeyOfRepresentationToAttribute:@"boyID"];
…

[puttin]

Update workaround with more detail

Why the workaround above not working:

@interface PenName: NSManagedObject
    @property (nonatomic, retain) NSNumber* peopleID;
    @property (nonatomic, retain) NSString* penName;
    @property (nonatomic, retain) NSString* type;
    @property (nonatomic, retain) People* people;
@end

@interface People: NSManagedObject
    @property (nonatomic, retain) NSString* realName;
@end

@interface Boy: People
    @property (nonatomic, retain) NSNumber* boyID;
@end

JSON:

{
    "boy": {
        "1": "Jack"
    }
}

Mappings:

RKEntityMapping* penNameMapping = [RKEntityMapping mappingForEntityForName:@"PenName" inManagedObjectStore:managedObjectStore];
penNameMapping.identificationAttributes = @[ @"peopleID", @"penName" ];
[penNameMapping addAttributeMappingFromKeyOfRepresentationToAttribute:@"peopleID"];
[penNameMapping addAttributeMappingsFromDictionary:@{@"{peopleID}": @"penName"}];
[penNameMapping addPropertyMapping:[RKRelationshipMapping relationshipMappingFromKeyPath:nil toKeyPath:@"people" withMapping:[Boy boyMapping]]];

+ [Boy boyMapping]:

RKEntityMapping* boyMapping = [RKEntityMapping mappingForEntityForName:@"Boy" inManagedObjectStore:managedObjectStore];
boyMapping.identificationAttributes = @[@"boyID"];
[boyMapping addAttributeMappingFromKeyOfRepresentationToAttribute:@"boyID"];

This will not work because RKObjectContainsValueForMappings(id representation, NSArray *propertyMappings) cannot deal with the RKObjectMappingNestingAttributeKeyName

---

Tricky workaround:

@implementation Boy (Tricky)
- (NSString *)trickyThing
{
    return nil;
}
- (void)setTrickyThing:(NSString *)trickyThing
{
    //nothing happen here
}
@end

then edit the + [Boy boyMapping] to + [Boy boyMappingWithBoyID:(NSString *)boyIDString]

RKEntityMapping* boyMapping = [RKEntityMapping mappingForEntityForName:@"People" inManagedObjectStore:managedObjectStore];
peopleMapping.identificationAttributes = @[@"boyID"];
[boyMapping addAttributeMappingFromKeyOfRepresentationToAttribute:@"boyID"];
//the tricky ↓
[boyMapping addAttributeMappingsFromDictionary:@{boyIDString: @"trickyThing"}];

Then the dynamic JSON format can be parsed correctly.

---

The main problem is when some one need to add relationship from the dynamic JSON with such abstract & child entity , the addConnectionForRelationship:connectedBy: is not working

[puttin]

Summary:
So I find two problems:

• addConnectionForRelationship:connectedBy: is not working with abstract & child entity
• RKObjectContainsValueForMappings inside the applyRelationshipMappings will destroy expectation with above case
  • addAttributeMappingFromKeyOfRepresentationToAttribute with dynamic attribute
  • nil sourceKeyPath RKRelationshipMapping with dynamic attribute
  • RKObjectContainsValueForMappings continue the for (RKRelationshipMapping *relationshipMapping in [self relationshipMappings]) inside applyRelationshipMappings without mapping