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    <p>Well, I'm not sure I understand your question, but I'll try and answer in the context of a simple domain model.</p> <p>Let's say you have a <code>Person</code> class and a <code>Computer</code> class, both extend <code>NSManagedObject</code>. <code>Person</code> is linked to <code>Computer</code> via a one-way relationship, a NSSet named <code>computers</code>.</p> <p>This would allow you to say in your code:</p> <pre><code>Person *person = // ... (loaded from database) NSSet *computers = person.computers; for (Computer *computer : computers) { // do something fun } </code></pre> <p>However, since it's a one-way relationship, you would <em>not</em> be able to do this:</p> <pre><code>Computer *computer = // loaded from DB Person *person = computer.person; // This line won't work </code></pre> <p>Therefore, since it won't work -- there's no backwards relationship -- the only way to get the related Person class would be to build a Fetch Request to query the database and find the Person instances that have the Computer as a member.</p> <pre><code>NSFetchRequest *fetchRequest = [[NSFetchRequest alloc] init]; NSPredicate *predicate = // define your NSPredicate to find the Person object here [fetchRequest setPredicate:predicate]; NSError *error = nil; NSArray *fetchedObjects = [context executeFetchRequest:fetchRequest error:&amp;error]; [fetchRequest release]; </code></pre> <p>Generally speaking, that's <em>annoying</em>. So, it's generally a good idea to define your relationships bi-directionally (e.g. with inverse) if possible, that would enable you to just do:</p> <pre><code>Person *person = computer.person; </code></pre>
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    1. POWhat's the Relationship Between Fetch and One Way Relationship in Core Data?
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    1. POWhat's the Relationship Between Fetch and One Way Relationship in Core Data?
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    1. COThat makes a lot of sense. Gee.
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    2. COI am still missing something. Say I still want to have person to computer a one way relationship. Say the way to do so without getting conmpiler error would be to define computer not as relationship but as fetch relationship. Hence, there is no person that owns computer. We don't have relationship between person to computer. We have fetch relationship between person to computer. So your predicate won't work.
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    3. COFetch relationships are ones that are calculated - they aren't physically represented in the data saved in the database. They are useful for things like sorting the results and/or only returning a subset - for example, you could have a fetch relationship from Person -> Computer, called `appleComputers` that only returns those computers who are owned by this person and `where make = "Apple"`.
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