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POAttribute of relationship in Core Data is returning nil when being called in iOS
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  1. POAttribute of relationship in Core Data is returning nil when being called in iOS
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    copied!<p>I have an iOS application where I am using Core Data for storage. I have two entities ("MyEntity", and "OtherEntity") which are in a one to one relationship. Both entities are related to each other (i.e. each entity has an inverse relationship with the other). In addition to having a relationship with each other, one of the attributes of each entity is also the primarykey of the other entity. The problem I am having is that I realize that I shouldn't have an attribute that is the foreign key of another entity, when the entities have a relationship with each other, however I am unable to retrieve the primary key indirectly by referencing the relationship attribute, but I am able to retrieve it by referencing the attribute that I explicitly set to the primary key of the other entity:</p> <pre><code>//NSInteger userId = [testUser.otherEntity.userId integerValue]; --&gt; returns nil NSInteger userId = [testUser.userId integerValue]; --&gt; works fine </code></pre> <p>where "testUser" is an instance of type "MyEntity" which is a subclass of NSManagedObject, and "otherEntity" is an instance of the Entity, "OtherEntity" that has an inverse relationship with "MyEntity".</p> <p>Here are the attributes of each Entity:</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; #import &lt;CoreData/CoreData.h&gt; @class OtherEntity; @interface MyEntity : NSManagedObject @property (nonatomic, strong) NSString * email; @property (nonatomic, strong) NSNumber * primaryId; //primary key for MyEntity @property (nonatomic, strong) NSString * metaData; @property (nonatomic, strong) NSDate * birthDate; @property (nonatomic, strong) NSString * name; @property (nonatomic, strong) NSNumber * userId; //this is the primary key for OtherEntity @property (nonatomic, strong) OtherEntity *otherEntity; @end </code></pre> <p>and here are the attributes for OtherEntity:</p> <pre><code>#import &lt;Foundation/Foundation.h&gt; #import &lt;CoreData/CoreData.h&gt; @class MyEntity; @interface OtherEntity : NSManagedObject @property (nonatomic, strong) NSString * address; @property (nonatomic, strong) NSString * city; @property (nonatomic, strong) NSString * country; @property (nonatomic, strong) NSString * fax; @property (nonatomic, strong) NSString * phone; @property (nonatomic, strong) NSString * postalCode; @property (nonatomic, strong) NSString * province; @property (nonatomic, strong) NSNumber * myUserId//primary key of MyEntity @property (nonatomic, strong) NSNumber * userId;//primary key of Other Entity @property (nonatomic, strong) MyEntity *myEntity; @end </code></pre> <p>Can anyone explain to me what the problem is, or what it is that I'm doing wrong?</p> <p>Thanks in advance to all who reply.</p>
 

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