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POCore data getting result based on entity count of relationship
 

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  1. POCore data getting result based on entity count of relationship
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    <p>I am new to core data and i dont know how to write query like this using core data.</p> <p>I hav two entities Album and Songs in schema. Album is related to Song by one many relationship and relationship name is tracks. I hav written query to fetch all albums and that is working well. But now i want to make little change in that so that i will not get albums having 0 songs. I tried to set predicate on request like </p> <pre><code>tracks.@count != 0 tracks.@count != nil </code></pre> <p>but this is not working may be because of faulting ?. Do i need to prefetch relationship or something. I dont want to add attribute songCount in Album and i just need count song. What is best way to write query like this ? thanks in advance !</p> <p>Code -</p> <pre><code>NSFetchRequest *request = [[NSFetchRequest alloc] init]; request.entity = [NSEntityDescription entityForName:@"Album" inManagedObjectContext:[self managedObjectContext]]; NSSortDescriptor *sort = [[NSSortDescriptor alloc] initWithKey:@"name" ascending:YES selector:@selector(caseInsensitiveCompare:)]; [request setSortDescriptors:[NSArray arrayWithObject:sort]]; NSPredicate *albumPredicate = [NSPredicate predicateWithFormat:@"tracks.@count &gt; 0"]; [request setPredicate:albumPredicate]; </code></pre> <p>This is what i got on console after turning on Debug mode</p> <pre><code>CoreData: sql: SELECT 0, t0.Z_PK FROM ZALBUM t0 WHERE (SELECT COUNT(*) FROM ZTRACK t1 WHERE (t0.Z_PK = t1.ZALBUM) ) &gt; ? ORDER BY t0.ZNAME COLLATE NSCollateNoCase </code></pre> <p>whats wrong in code ?</p>
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    1. USAditya Deshmane
    1. USAditya Deshmane
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      1. VTUpMod
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      1. VTUpMod
    1. CO`tracks.@count != 0` should just work.
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      1. USMartin R
    2. COIt'd help if you'd include your code and a better description of the problem. *this is not working* really isn't enough to let us help you figure out *why* it's not working.
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      1. USCaleb
 

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