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How to get a sum for a particular attribute in a CoreData DB?

 原文  2012-06-21 09:22:48  9   1    ios/ core-data/ nsfetchrequest/ nsentitydescription

Question

I recently have just been able to populate my core data DB. I have an attribute named username and I would like to get the total number of users on the system (in the DB) and print it out. I know I need to use NSFetchRequest along with NSEntityDescription . I am just not sure how to go about it. I haven't really seen a question like this on SO. The entity is named Account and my attribute is labeled username

1 answers

solution1
 2 ACCPTED  2012-06-21 09:27:35

对于您的特定情况，我假设您将每个用户名作为单独的记录，因此您可以使用-countForFetchRequest:error: NSManagedObjectContext方法来获取给定获取请求如果已传递给executeFetchRequest:error:将返回的对象数executeFetchRequest:error:

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