如何验证实体的NSMutableArray是否包含具有特定属性的对象

Question

Based on the data model here: Photographer<------->>Photo

When the user goes to add a Photo , the user also specifies what Photographer took said picture. When the user decides to save the Photo , there is the possibility that the Photographer doesn't exist yet. After executing a NSFetchRequest to get a list of all instances of Photographer , how do I check if the NSMutableArray(photographerArray) contains an object that has the same fullName attribute as what the user is currently adding?

Answer 1

The naive way would be to simply get all the fullName of the array and check if it's in it.

BOOL photographerExist = [[listOfPhotographer valueForKey:@"fullName"] containsObject:enteredFullName];

However, it would be way more easier to put that directly in your fetch request. Just add a predicate to it.

NSPredicate *fullNamePredicate = [NSPredicate predicateWithFormat:@"fullName = %@", enteredFullName];
fetchRequest.predicate = fullNamePredicate;

If the result of the fetch is empty, then the photographer doesn't exist yet.