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PORestKit many to many relationship saves new rows in both join table and null values in main table
 

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  1. PORestKit many to many relationship saves new rows in both join table and null values in main table
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    <p>I use RestKit to cache data from a remote server locally. In it I have a many to many relationship between Category &lt;&lt;-->> News. The mapping seems to work properly, despite that it also saves null values in my Category table (it saves the correct categories too). Like the image below:</p> <p><img src="https://i.stack.imgur.com/1WSdP.png" alt="enter image description here"></p> <p>It seems to save 30 null rows, I also have 30 (not null) rows in my join table so there might be a correlation here. </p> <p>The JSON that I get looks like this: <code>"categories":[{"category_id":1},{"category_id":4}]</code></p> <p>I have two custom model objects that inherits from <code>NSManagedObject</code>. </p> <pre><code>@interface News : NSManagedObject [...] @property (nonatomic, retain) NSSet *categories; @end @interface Category : NSManagedObject [...] @property (nonatomic, retain) NSSet *news; @end </code></pre> <p>I use <code>@dynamic</code> on both. </p> <p>My mappings looks like this: </p> <pre><code>RKManagedObjectMapping *categoryMapping = [RKManagedObjectMapping mappingForClass:[Category class] inManagedObjectStore:objectManager.objectStore]; categoryMapping.primaryKeyAttribute = @"categoryId"; categoryMapping.rootKeyPath = @"categories"; [categoryMapping mapKeyPath:@"id" toAttribute:@"categoryId"]; [...] RKManagedObjectMapping* newsMapping = [RKManagedObjectMapping mappingForClass:[News class] inManagedObjectStore:objectManager.objectStore]; newsMapping.primaryKeyAttribute = @"newsId"; newsMapping.rootKeyPath = @"news"; [newsMapping mapKeyPath:@"id" toAttribute:@"newsId"]; [...] // Categories many-to-many (not fully working yet). [newsMapping mapKeyPath:@"categories" toRelationship:@"categories" withMapping: categoryMapping]; // Register the mappings with the provider [objectManager.mappingProvider setObjectMapping:newsMapping forResourcePathPattern:@"[path-to-JSON]"]; [objectManager.mappingProvider setObjectMapping:categoryMapping forResourcePathPattern:@"[path-to-JSON]"]; </code></pre> <p>I fetch the data like this (much like the Twitter RestKit example):</p> <pre><code>- (id)init { self = [super init]; if (self) { [self loadCategories]; [self loadCategoriesFromDataStore]; [self loadNews]; [self loadNewsFromDataStore]; } return self; } - (void)loadCategoriesFromDataStore { NSFetchRequest* request = [Category fetchRequest]; NSSortDescriptor* descriptor = [NSSortDescriptor sortDescriptorWithKey:@"categoryId" ascending:YES]; [request setSortDescriptors:[NSArray arrayWithObject:descriptor]]; _categories = [Category objectsWithFetchRequest:request]; } - (void)loadNewsFromDataStore { NSFetchRequest* request = [News fetchRequest]; NSSortDescriptor* descriptor = [NSSortDescriptor sortDescriptorWithKey:@"createdAt" ascending:NO]; [request setSortDescriptors:[NSArray arrayWithObject:descriptor]]; _news = [News objectsWithFetchRequest:request]; } - (void)loadCategories { // Load the object model via RestKit RKObjectManager *objectManager = [RKObjectManager sharedManager]; [objectManager loadObjectsAtResourcePath:@"[link-to-JSON]" delegate:self]; } - (void)loadNews { // Load the object model via RestKit RKObjectManager *objectManager = [RKObjectManager sharedManager]; [objectManager loadObjectsAtResourcePath:@"[link-to-JSON]" delegate:self]; } - (void)objectLoader:(RKObjectLoader*)objectLoader didLoadObjects:(NSArray*)objects { [[NSUserDefaults standardUserDefaults] synchronize]; [self loadCategoriesFromDataStore]; [self loadNewsFromDataStore]; } </code></pre> <p>Any ideas what I'm doing wrong? </p> <p><strong>Note:</strong> It also seems to save 30 rows to the join table when there are 15 News, I don't know if this is the normal behavior for join tables. </p> <p><strong>Update:</strong> It also maps the the wrong category id's in the join table (ie. category 66, a null row). </p> <p><strong>update 2:</strong> JSON get request for my Category {"categories":{[...], "id":1, [...]}</p>
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    1. USAnders
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    1. COCan you use the following line and tell me what number it returns: NSNumber* count = [Category numberOfEntities];. If this returns 30 then everything is fine. Forget about the relationship (join) table, core data should manage that correctly if your mapping is correct. NSNumber* news = [News numberOfEntities] should also be 15.
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      1. USPaul de Lange
    2. CONews returns 15, and seems to work. But Category first (on clean database) returns 36 (there should be 6 categories from the JSON), the second time I run it is 66 etc. And the values is NULL.
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